boards: silabs: Add xgm240_rb4316a and xgm240_rb4317a

Add support for xGM240-RB4316A and xGM240-RB4317A radio boards
for xGM240 modules. The two boards share pinout configuration, but
have different radio and power configurations.

Signed-off-by: Aksel Skauge Mellbye <aksel.mellbye@silabs.com>
16 files changed