ksmbd: remove unneeded check_context_err

Coverity Scan seems to report false alarm.

*** CID 1505930:    (USE_AFTER_FREE)
/fs/ksmbd/smb2pdu.c: 2527 in smb2_open()
>>> CID 1505930:    (USE_AFTER_FREE)
>>> Passing freed pointer "context" as an argument to
>>> "check_context_err".

This patch remove unneeded check_context_err to make coverity scan
happy.

Reported-by: Coverity Scan <scan-admin@coverity.com>
Signed-off-by: Namjae Jeon <namjae.jeon@samsung.com>
Signed-off-by: Steve French <stfrench@microsoft.com>