serial: cadence: Add generic earlycon support

Add earlycon support for the cadence serial port.
This is based on recent patches:
"tty/serial: pl011: add generic earlycon support"
(sha1: 0d3c673e7881e691991b2a4745bd4f149603baa2)
"tty/serial: add arm/arm64 semihosting earlycon"
(sha1: d50d7269ebcb438afa346cdffce0f4e2a1b9e831)

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --cc Documentation/kernel-parameters.txt
Simple merge

diff --cc drivers/tty/serial/Kconfig
Simple merge

diff --cc drivers/tty/serial/xilinx_uartps.c
Simple merge