spi: pxa2xx: Set the max_speed_hz of the master

Carry input clock of the controller in max_speed_hz of struct spi_master
instead of in own driver data. They mean the same thing and more over now
the max_speed_hz is not even set here.

As an added bonus this allows SPI core to validate that transfer speed is
not beyond the maximum input clock. This is not a problem in spi-pxa2xx as
the driver doesn't use transfer speed parameter directly but via input
clock divider calculation which will top at divide by one. However it's
better to validate speed before passing it here.

Signed-off-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>