drivers/video/ep93xx-fb.c: include <linux/io.h> for devm_ioremap()

Commit be867814 ("drivers/video/ep93xx-fb.c: use devm_ functions")
introduced a build error:

  drivers/video/ep93xx-fb.c: In function 'ep93xxfb_probe':
  drivers/video/ep93xx-fb.c:532: error: implicit declaration of function 'devm_ioremap'
  drivers/video/ep93xx-fb.c:533: warning: assignment makes pointer from integer without a cast

Include <linux/io.h> to pickup the declaration of 'devm_ioremap'.

Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Cc: Florian Tobias Schandinat <FlorianSchandinat@gmx.de>
Acked-by: Ryan Mallon <rmallon@gmail.com>
Cc: Damien Cassou <damien.cassou@lifl.fr>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>