[ARM] 5582/1: VIC: support ST-modified version with a split init

The Nomadik SoC (not yet merged) has a modified PL090 VIC cell. This adds
support for it by reading the PrimeCell ID at the end of the page and
calling a separate init function.

Signed-off-by: Alessandro Rubini <rubini@unipv.it>
Acked-by: Andrea Gallo <andrea.gallo@stericsson.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>