[ARM] 5222/1: Allow configuring user:kernel split via Kconfig

This patch adds a config option (CONFIG_VMSPLIT_*) to allow choosing
between 3:1, 2:2 and 1:3 user:kernel memory splits.

Tested-by: Riku Voipio <riku.voipio@iki.fi>
Signed-off-by: Lennert Buytenhek <buytenh@marvell.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>