drivers/dma/: Use the ccflag-y instead of EXTRA_CFLAGS

Use the ccflag-y flag instead of EXTRA_CFLAGS because EXTRA_CFLAGS is
deprecated and should now be switched. According to (documentation/kbuild/makefiles.txt).

Signed-off-by: Tracey Dent <tdent48227@gmail.com>
Acked-by: Linus Walleij <linus.walleij@stericsson.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>