[ARM] 5523/1: ep93xx phys offset selection

This patch adds a Kconfig option to select between ep93xx boards which
boot from the SDRAM bank at 0x00000000 (SDCE3/SyncBoot) and those which
boot from 0xc0000000 (SDCE0). This corrects a problem which causes
invalid images to be built for boards which boot from 0xc0000000.

Signed-off-by: Ryan Mallon <ryan@bluewatersys.com>
Acked-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>