lightnvm: remove checkpatch warning for unsigned ints

Checkpatch found two incidents where the type was preferred to be
written out in full.

./drivers/lightnvm/rrpc.h:184: WARNING: Prefer 'unsigned int' to bare
use of 'unsigned'
./drivers/lightnvm/rrpc.h:209: WARNING: Prefer 'unsigned int' to bare
use of 'unsigned'
./drivers/lightnvm/rrpc.c:51: WARNING: Prefer 'unsigned int' to bare use
of 'unsigned'

Signed-off-by: Matias Bjørling <m@bjorling.me>
Signed-off-by: Jens Axboe <axboe@fb.com>