pcmcia: pxa2xx: update socket driver to use devm_clk_get() API

Update the pxa2xx socket driver to use the devm_clk_get() API so that
the cleanup paths are simplified.

Reviewed-by: Robert Jarzmik <robert.jarzmik@free.fr>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>