Two issues caused the sensitivity on CC13xx devices to be dramatically
worse than CC26xx devices:
* Wrong front-end mode configuration
* Faulty/outdated RF switching logic
Both issues are inherently board-specific. Therefore, a generic
configuration was aligned across all boards which allows a specific
board to configure a correct RF front-end mode. In addition, the RF
switching logic was updated to latest and greatest.
All LaunchPads drives the UART0_RX pin up, but is configured in the
Board file to be pull-down. This alignes the UART0_RX pin configuration
with the development board HW.
This commit changes the method of accessing the default v6 prefix. Instead of always using `UIP_DS6_DEFAULT_PREFIX`, we store the default prefix in a variable. We subsequently retrieve the prefix by calling `uip_ds6_default_prefix()`.
`uip_ds6_init()` will set this variable to the value of `UIP_DS6_DEFAULT_PREFIX`, but only if the startup code has not set a different default prefix before `uip_ds6_init()` gets called.
This approach has the following benefits:
* It allows us to change the default prefix at run time.
* It allows the startup code to set a prefix different than the one specified by `UIP_DS6_DEFAULT_PREFIX`, which can be useful if the default prefix comes from a different source (e.g. the command line for native, or a configuration stored on a node's flash)
* In many places the current code assumes that the prefix contains 6 bytes of zeros (e.g. `FDxx::/64`). Changing to a different prefix (e.g. `FD00:ABCD::`) would need extensive code changes. This change here makes it easy to use a prefix of any length.
With the exception of one specific build configuration for platform nrf52dk, all our arm-based platforms use the debugging I/O library from os/lib/dbg-io. This commit changes the build system to include this module by default for all arm devices. Platform / CPU Makefiles will no longer need to request this MODULE explicitly. Configuration provided to allow exclusion where required, as is the case for nrf52dk when NRF52_USE_RTT is set to 1.
If BOARD is unspecified, simplelink platform's build system will generate an error instead of choosing a default. This is a) inconsistent with what we do for other platforms and b) problematic because making targets clean, distclean etc will fail.
