[media] drivers/staging/media/as102: using ccflags-y instead of EXTRA_FLAGS in Makefile

need using ccflags-y instead of EXTRA_CFLAGS
    can reference scripts/checkpatch.pl (1755..1766)
  when make EXTRA_CFLAGS=-W, the compiling issue will be occured.

Signed-off-by: Chen Gang <gang.chen@asianux.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>