cifs: address unused variable warning

Fix trivial unused variable warning (when SMB1 support disabled)

"ioctl.c:324:17: warning: variable 'caps' set but not used [-Wunused-but-set-variable]"

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202305250056.oZhsJmdD-lkp@intel.com/


Signed-off-by: Steve French <stfrench@microsoft.com>