mmc: sdhci-pxav3: Remove checks for mandatory host clock

NULL-checking a struct clk it not only wrong but also not required as
for PXAv3 driver the corresponding clock is mandatory. Remove the
checks from sdhci_pxav3_runtime_{suspend,resume}.

Signed-off-by: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>