ARM: mach-shmobile: Initial AG5 and AG5EVM support

This patch adds initial support for Renesas SH-Mobile AG5.

At this point the AG5 CPU support is limited to the ARM
core, SCIF serial and a CMT timer together with L2 cache
and the GIC. The AG5EVM board also supports Ethernet.

Future patches will add support for GPIO, INTCS, CPGA
and platform data / driver updates for devices such as
IIC, LCDC, FSI, KEYSC, CEU and SDHI among others.

The code in entry-macro.S will be cleaned up when the
ARM IRQ demux code improvements have been merged.

Depends on the AG5EVM mach-type recently registered but
not yet present in arch/arm/tools/mach-types.

As the AG5EVM board comes with 512MiB memory it is
recommended to turn on HIGHMEM.

Many thanks to Yoshii-san for initial bring up.

Signed-off-by: Magnus Damm <damm@opensource.se>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>