scsi: zfcp: drop default switch case which might paper over missing case

[ Upstream commit 0c902936e55cff9335b27ed632fc45e7115ced75 ]

This was introduced with v4.18 commit 8c3d20aa ("scsi: zfcp: fix
missing REC trigger trace for all objects in ERP_FAILED") but would now
suppress helpful -Wswitch compiler warnings when building with W=1 such as
the following forced example:

drivers/s390/scsi/zfcp_erp.c: In function 'zfcp_erp_handle_failed':
drivers/s390/scsi/zfcp_erp.c:126:2: warning: enumeration value 'ZFCP_ERP_ACTION_REOPEN_PORT_FORCED' not handled in switch [-Wswitch]
  switch (want) {
  ^~~~~~

But then again, only with W=1 we would notice unhandled enum cases.
Without the default cases and a missed unhandled enum case, the code might
perform unforeseen things we might not want...

As of today, we never run through the removed default case, so removing it
is no functional change.  In the future, we never should run through a
default case but introduce the necessary specific case(s) to handle new
functionality.

Signed-off-by: Steffen Maier <maier@linux.ibm.com>
Reviewed-by: Benjamin Block <bblock@linux.ibm.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>