[ARM] 4747/1: pcm027: support for pcm990 baseboard for phyCORE-PXA270

This patch adds baseboard support for the phyCORE-PXA270 development
kit (aka PCM-990).

This example shows how to use some phyCORE-PXA270 CPU module features
on a baseboard in a standard manner. It could be used as a starting
point for custom baseboard development.

V2:
 After comments by Eric Miao:
  - IRQ chained handler fixed
  - video/graphic support moved to separate patch
  - ifdef/endif hell reduced ;-)

V3:
 After comments by Russell King
  - initialise the mmci platform data statically

V4:
 After comments by Russell King
  - wrong return value in pcm990_mci_init() fixed

Signed-off-by: Juergen Beisert <j.beisert@pengutronix.de>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>