[ARM] 4785/1: S3C24XX: Add _SHIFT definitions for S3C2410_BANKCON registers

Add definitions to allow easier decomposotion of the contents of
the S3C2410_BANKON registers

Signed-off-by: Ben Dooks <ben-linux@fluff.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>