scsi: ufs: core: Improve return value documentation

scsi: ufs: core: Improve return value documentation

Some functions return a negative value to indicate an error while other
functions return a value != 0 to indicate an error. Document the return
value behavior where this documentation is missing and fix the return
value documentation where necessary. Add warnings to detect mismatches
between documentation and implementation. This matters because several
sysfs callback functions only work correctly if a negative value is
returned upon error.

Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Link: https://lore.kernel.org/r/20250623215909.4169007-1-bvanassche@acm.org
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>