cifs: enable fscache iff fsc mount option is used explicitly

Currently, if CONFIG_CIFS_FSCACHE is set, fscache is enabled on files opened
as read-only irrespective of the 'fsc' mount option. Fix this by enabling
fscache only if 'fsc' mount option is specified explicitly.

Remove an extraneous cFYI debug message and fix a typo while at it.

Reported-by: Jeff Layton <jlayton@redhat.com>
Acked-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Suresh Jayaraman <sjayaraman@suse.de>
Signed-off-by: Steve French <sfrench@us.ibm.com>