Without this header, we get a build error in some configurations:
drivers/media/platform/omap/omap_vout_vrfb.c: In function 'omap_vout_setup_vrfb_bufs':
drivers/media/platform/omap/omap_vout_vrfb.c:143:26: error: implicit declaration of function 'kzalloc'; did you mean 'vzalloc'? [-Werror=implicit-function-declaration]