ARM: vexpress: refactoring of Versatile Express CA9x4 support

The current ca9x4_ct_vxp platform contains support for a Versatile
Express motherboard with a quad core A9 core tile.

This patch separates the Versatile Express motherboard code and the
A9 specific code, to ease supporting more core tiles in the next
patches.

Andre: merged the first two of Ryan's original patches and did some
checkpatch fixes.

Signed-off-by: Ryan Harkin <ryan.harkin@linaro.org>
Signed-off-by: Andre Przywara <andre.przywara@linaro.org>