drivers: cadence: cdns: Update CDNS driver to support MULTI_CONSOLE_API ...

This patch updates the Cadence CDNS console driver to support the new
console API. The driver will continue to support the old API as well by
checking the MULTI_CONSOLE_API compile-time flag.

Change-Id: I2ef8fb0d6ab72696997db1e0243a533499569d6b
Signed-off-by: Julius Werner <jwerner@chromium.org>

Use SPDX license identifiers ...

To make software license auditing simpler, use SPDX[0] license
identifiers instead of duplicating the license text in every file.

NOTE: Files that have been imported by FreeBSD have not been modified.

[0]: https://spdx.org/

Change-Id: I80a00e1f641b8cc075ca5a95b10607ed9ed8761a
Signed-off-by: dp-arm <dimitris.papastamos@arm.com>

Add console_core_flush() in upstream platforms ...

It is needed to add placeholders for this function because, as this is
not a `plat_xxx()` function, there aren't weak definitions of it in any
file.

If `console_flush()` is used and there isn't an implementation of
`console_core_flush()` in any file, the compilation will fail.

Change-Id: I50eb56d085c4c9fbc85d40c343e86af6412f3020
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>

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

drivers: Add Cadence UART driver ...

Add a driver for the Cadence UART which is found in Xilinx Zynq SOCs.

Signed-off-by: Soren Brinkmann <soren.brinkmann@xilinx.com>