Move console drivers to AArch64 folder ...

This patch moves the various assembly console drivers
into `aarch64` architecture specific folder. Stub files,
which include files from new location, are retained at the
original location for platform compatibility reasons.

Change-Id: I0069b6c1c0489ca47f5204d4e26e3bc3def533a8

Use uintptr_t as base address type in ARM driver APIs ...

This patch changes the type of the base address parameter in the
ARM device driver APIs to uintptr_t (GIC, CCI, TZC400, PL011). The
uintptr_t type allows coverage of the whole memory space and to
perform arithmetic operations on the addresses. ARM platform code
has also been updated to use uintptr_t as GIC base address in the
configuration.

Fixes ARM-software/tf-issues#214

Change-Id: I1b87daedadcc8b63e8f113477979675e07d788f1

Separate out common console functionality ...

Separate out the common console functionality in
`drivers/arm/pl011/pl011_console.S` into a new source file
`drivers/console/console.S`. The former includes the latter to
provide backwards compatibility for platform make files.

Also add a skeleton console implementation for platforms that do not
want to use PL011.

Change-Id: I1ff963b2b54a872fbcf1eb0700797b9e9afa2538