common: board_r: drop initr_kgdb wrapper

Add a return value to kgdb_init and use it directly in the post-relocation
init sequence, rather than using a wrapper stub. Also, move the "KGDB"
print message inside kgdb_init().

Reviewed-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Ovidiu Panait <ovidiu.panait@windriver.com>