bluetooth: controller: rv32m1: configure debug pins in DEBUG_INIT

The debug pins were configured in a board specific file, however, the
subsys/bluetooth/controller/ll_sw/openisa/hal/RV32M1/debug.h file
already contains board-specific pins, meaning there's no need to split
the information in 2 places. Move the GPIO configuration calls to the
DEBUG_INIT() macro in the controller debug header.

Note that in the future, Devicetree should be used to provide a
hardware-agnostic debug module.

Signed-off-by: Gerard Marull-Paretas <gerard.marull@nordicsemi.no>