scsi: scsi_debug: Remove unused variable sdebug_any_injecting_opt

scsi: scsi_debug: Remove unused variable sdebug_any_injecting_opt

The static variable sdebug_any_injecting_opt is no longer read. Commit
3a90a63d02b8 ("scsi: scsi_debug: every_nth triggered error injection")
removed all code that reads this variable. Hence, also remove this
variable itself. Remove SDEBUG_OPT_ALL_INJECTING because there is no
code left that uses this constant if sdebug_any_injecting_opt is
removed. This has been detected by building the scsi_debug driver with
the git HEAD version of Clang and with W=1.

Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: John Garry <john.g.garry@oracle.com>
Link: https://patch.msgid.link/20260520171454.4035623-1-bvanassche@acm.org
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>