mmc: sdhci-of-arasan: refactor set_clock callback

mmc: sdhci-of-arasan: refactor set_clock callback

commit 61b914eb81f8 ("mmc: sdhci-of-arasan: add phy support for
sdhci-of-arasan") introduce phy support for arasan. According to
the vendor's databook, we should make sure the phy is in poweroff
stat before we configure the clk stuff. Otherwise it may cause
some IO sample timing issue from the test. But we don't need this
extra operation while running in non HS200/HS400 mode since phy
doesn't trigger sampling block.

Change-Id: I5506f99e5a3b4d9a4356ad485ceac900c6d754aa
Signed-off-by: Shawn Lin <shawn.lin@rock-chips.com>