ARM: 6475/1: Introduce asm/hardware/entry-macro-gic.S

This patch is the identical GIC demux implementation
merge V3. Instead of implementing same code over and
over simply share it in entry-macro-gic.S. The shared
code is based on the realview implementation.

Each GIC demux instance still has to setup the base address
of the controller using the get_irqnr_preamble macro. The
rest of the GIC specific code can be shared.

Signed-off-by: Magnus Damm <damm@opensource.se>
Acked-by: Srinidhi Kasagar <srinidhi.kasagar@stericsson.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>