kernel: owl-loader: fix sparse endian warnings

kernel: owl-loader: fix sparse endian warnings

owl-loader.c:83:21: sparse: warning: incorrect type in assignment (different base types)
owl-loader.c:83:21: sparse:    expected unsigned short [usertype] reg
owl-loader.c:83:21: sparse:    got restricted __be16 const [usertype] reg
owl-loader.c:84:21: sparse: warning: incorrect type in assignment (different base types)
owl-loader.c:84:21: sparse:    expected unsigned int [usertype] val
owl-loader.c:84:21: sparse:    got restricted __be16 const [usertype] low_val
owl-loader.c:85:28: sparse: warning: restricted __be16 degrades to integer

Reported-by: kbuild test robot
Signed-off-by: Christian Lamparter <chunkeey@gmail.com>