Introduce console_uninit() API in ARM Trusted Firmware ...

Allowing console base address to be set to NULL conveniently
allows console driver to ignore further invocations to console_putc()
and console_getc(). This patch adds `console_uninit()` API to the
console driver which sets console base address as NULL. The BL images can
invoke this API to finish the use of console and ignore any further
invocations to print to the console.

Change-Id: I00a1762b3e0b7c55f2be2f9c4c9bee3967189dde

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