mmc: sdhci-of-arasan: remove disable clk_ahb from sdhci_arasan_resume

We don't really need disable clk_ahb when failing to resume. Otherwise
we may take risk of bus error for accessing register without clk_ahb.

Signed-off-by: Shawn Lin <shawn.lin@rock-chips.com>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>