ARM: 7717/1: mmc: mmci: Use devm_clk_get API

Converting to devm_clk_get simplifies error handling in probe
and we can remove other corresponding calls to clk_put.

Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>