staging/atomisp: fix returnvar.cocci warnings

drivers/staging/media/atomisp/pci/atomisp2/./atomisp_ioctl.c:560:5-8: Unneeded variable: "ret". Return "0" on line 577

 Remove unneeded variable used to store return value.

Generated by: scripts/coccinelle/misc/returnvar.cocci

Signed-off-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>