ARM : i.MX27 : split code for allocation of ressources of camera and eMMA

This is to prepare addition of m2m-emmapp driver otherwise
IMX_HAVE_PLATFORM_MX2_CAMERA must be declared even if only Post-Processor is
needed.

IMX_HAVE_PLATFORM_MX2_EMMA define has been added.

Changes since v1:
 - Add "select IMX_HAVE_PLATFORM_MX2_EMMA" for MACH_IMX27_VISSTRIM_M10 platform
   due to pending patch in linux-media tree that will call
   imx27_add_mx2_emmaprp().

Signed-off-by: Gaëtan Carlier <gcembed@gmail.com>
Acked-by: Javier Martin <javier.martin@vista-silicon.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>