media: staging: atomisp: gc2235: constify acpi_device_id

acpi_device_id are not supposed to change at runtime. All functions
working with acpi_device_id provided by <acpi/acpi_bus.h> work with
const acpi_device_id. So mark the non-const structs as const.

File size before:
   text	   data	    bss	    dec	    hex	filename
  10754	   1360	      4	  12118	   2f56
drivers/staging/media/atomisp/i2c/gc2235.o

File size After adding 'const':
   text	   data	    bss	    dec	    hex	filename
  10818	   1296	      4	  12118	   2f56
drivers/staging/media/atomisp/i2c/gc2235.o

Signed-off-by: Arvind Yadav <arvind.yadav.cs@gmail.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>