target: fix match_token option in target_core_configfs.c

The match_token function does not recognize the option 'l',
so that both the mapped_lun and target_lun parameters
can not be resolved correctly.

And parsed u64-type parameters should use match_u64().

(Use %u instead of %s for Opt_mapped_lun + Opt_target_lun - nab)

Signed-off-by: tangwenji <tang.wenji@zte.com.cn>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>