earlycon: Remove hardcoded port->uartclk initialization in of_setup_earlycon

commit 182ead3e418a20328b73152b8e81fc8b4cac3b0b upstream.

There is no reason to initialize uartclk to BASE_BAUD * 16 for DT based
systems.

[-stable comment: commit 31cb9a85 ("earlycon: initialise baud field
 of earlycon device structure") has changed 8250_early.c behavior which
 now tries to setup UART speed.
 Already-backported upstream commit 0ff3ab701963 ("serial:  8250_early:
 Only set divisor if valid clk & baud") handles properly uartclk not
 being set but it still requires backporting fix for wrong uartclk val.
 This fixes malformed early console output on arch-es with BASE_BAUD.]

Fixes: 31cb9a85 ("earlycon: initialise baud field of earlycon device structure")
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Tested-by: Matt Redfearn <matt.redfearn@mips.com>
[rmilecki: add -stable comment and Fixes tag]
Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>