scsi: elx: efct: Fix pointer error checking in debugfs init

debugfs_create_xxx routines, which return pointers, are being checked for
error by looking for NULL values. The routines may return pointer-munged
-Exxx codes, so they should be using IS_ERR() to adapt.

There are two cases:

 - The first case is on initial directory creation, which actually doesn't
   need to be checked. So remove the check.

 - Creation of the sessions subdirectory. Modify this creation to create
   under the initial directory created, and fix failure check.

Link: https://lore.kernel.org/r/20210618233004.83769-1-jsmart2021@gmail.com


Fixes: 4df84e84 ("scsi: elx: efct: Driver initialization routines")
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: James Smart <jsmart2021@gmail.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>