drivers/pl011: Don't configure baudrate

drivers/pl011: Don't configure baudrate

The default baud and clock_hz configuration parameters are hardcoded
(commit 60ff9444480995008caf) for Versatile Express. Other platforms,
these default values may not be valid and might cause problems by
programming registers IBRD and FBRD incorrectly.

So, removing driver logic that sets the baudrate to fix the problem.
The behavior is unchanged because the driver was already relying on
the boot firmware for setting the correct baudrate.

Signed-off-by: Shanker Donthineni <shankerd@codeaurora.org>
Reviewed-by: Julien Grall <julien.grall@arm.com>
Signed-off-by: Stefano Stabellini <sstabellini@kernel.org>