Move USB sourcefiles to the CC2538 CPU dir

Previously, the CC2538 port would compile USB-related files from their original location under the CC2531 CPU dir. We are now removing the latter, but we need to keep those files.

arch/cpu/cc253x/usb/Makefile.usb

@@ -1,3 +0,0 @@
-USB_SOURCEFILES = usb-arch.c usb-core.c cdc-acm.c cdc-acm-descriptors.c
-CONTIKI_CPU_DIRS += usb usb/common usb/common/cdc-acm
-

arch/cpu/cc253x/usb/cdc-acm-descriptors.c

@@ -1,130 +0,0 @@
-#include "descriptors.h"
-#include "contiki.h"
-#include "cdc.h"
-#include "usb-arch.h"
-
-#if USB_CONF_CLASS == 1
-
-const struct usb_st_device_descriptor device_descriptor =
-  {
-    sizeof(struct usb_st_device_descriptor),
-    DEVICE,
-    0x0200,
-    CDC,
-    0,
-    0,
-    CTRL_EP_SIZE,
-    CDC_ACM_CONF_VID,
-    CDC_ACM_CONF_PID,
-    0x0000,
-    1,
-    2,
-    3,
-    1
-  };
-
-const struct configuration_st {
-  struct usb_st_configuration_descriptor configuration;
-  struct usb_st_interface_descriptor comm;
-  struct usb_cdc_header_func_descriptor header;
-  struct usb_cdc_abstract_ctrl_mgmnt_func_descriptor abstract_ctrl;
-  struct usb_cdc_union_func_descriptor union_descr;
-  struct usb_cdc_call_mgmnt_func_descriptor call_mgmt;
-#if 1
-  struct usb_st_endpoint_descriptor ep_notification;
-#endif
-  struct usb_st_interface_descriptor data;
-  struct usb_st_endpoint_descriptor ep_in;
-  struct usb_st_endpoint_descriptor ep_out;
-} BYTE_ALIGNED configuration_block =
-  {
-    /* Configuration */
-    {
-      sizeof(configuration_block.configuration),
-      CONFIGURATION,
-      sizeof(configuration_block),
-      2,
-      1,
-      0,
-      0x80,
-      250
-    },
-    {
-      sizeof(configuration_block.comm),
-      INTERFACE,
-      0,
-      0,
-      1,
-      CDC,
-      ABSTRACT_CONTROL_MODEL,
-      V_25TER_PROTOCOL,
-      0
-    },
-    {
-      sizeof(configuration_block.header),
-      CS_INTERFACE,
-      CDC_FUNC_DESCR_HEADER,
-      0x0110
-    },
-    {
-      sizeof(configuration_block.abstract_ctrl),
-      CS_INTERFACE,
-      CDC_FUNC_DESCR_ABSTRACT_CTRL_MGMNT,
-      0x2, // Set line coding
-    },
-    {
-      sizeof(configuration_block.union_descr),
-      CS_INTERFACE,
-      CDC_FUNC_DESCR_UNION,
-      0, /* Master */
-      {1}  /* Slave */
-    },
-    {
-      sizeof(configuration_block.call_mgmt),
-      CS_INTERFACE,
-      CDC_FUNC_DESCR_CALL_MGMNT,
-      0x00,
-      1 /* data interface */
-    },
-    {
-      sizeof(configuration_block.ep_notification),
-      ENDPOINT,
-      0x81,
-      0x03,
-      USB_EP1_SIZE,
-      255 /* 255ms polling, not really used so maximum value used */
-    },
-    {
-      sizeof(configuration_block.data),
-      INTERFACE,
-      1,
-      0,
-      2,
-      CDC_DATA,
-      0,
-      /*TRANSPARENT_PROTOCOL*/ 0,
-      0
-    },
-    {
-      sizeof(configuration_block.ep_in),
-      ENDPOINT,
-      0x82,
-      0x02,
-      USB_EP2_SIZE,
-      0
-    },
-    {
-      sizeof(configuration_block.ep_out),
-      ENDPOINT,
-      0x03,
-      0x02,
-      USB_EP3_SIZE,
-      0
-    }
-
-  };
-
-const struct usb_st_configuration_descriptor const *configuration_head =
-(struct usb_st_configuration_descriptor const*)&configuration_block;
-
-#endif