tty/serial: add back missing setup_early_serial8250_console

Commit d2fd6810a823bcd (tty/serial: convert 8250 to generic earlycon)
removed setup_early_serial8250_console, but there are still 2 callers
in:

arch/mips/mti-malta/malta-init.c
drivers/firmware/pcdp.c

Add back the function implemented as a wrapper to setup_earlycon.

Reported-by: Yinghai Lu <yinghai@kernel.org>
Cc: Jiri Slaby <jslaby@suse.cz>
Cc: linux-serial@vger.kernel.org

Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(cherry picked from commit fe1cf8af918af3ff0dd58ce92e5a5da117cb1d92)
Signed-off-by: Alex Shi <alex.shi@linaro.org>
(cherry picked from commit bd3132993d81a28b3a165ef6cc1abe0c4a0c6ac6)
Signed-off-by: Alex Shi <alex.shi@linaro.org>
tty/serial: fix 8250 early console option passing to regular console

In the conversion to generic early console, the passing of options from
the early 8250 console to the regular ttyS console was broken. This
resulted in the baud rate changing when switching consoles during boot.

This feature allows specifying a single console option on the kernel
command line rather than both an early console and regular serial tty
console. It would be nice to generalize this feature. However, it only
works if the correct baud rate can be probed early which is not the
case on many platforms which have non-standard UART clock rates. So for
now, this is left as an 8250 specific feature.

Reported-and-tested-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Rob Herring <robh@kernel.org>
Cc: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(cherry picked from commit 60efcf0414be5876d81276e3c1fd12680ba2ce71)
Signed-off-by: Alex Shi <alex.shi@linaro.org>
(cherry picked from commit 5eb6ba4882c9c0b3b83486ab66b0c9e68189de4b)
Signed-off-by: Alex Shi <alex.shi@linaro.org>
Merge remote-tracking branch 'v3.10/topic/earlycon' into linux-linaro-lsk