ARM: dts: msm: Revert gpio21 related change for QCS405

This change is to revert commit 0448c578 ("ARM: dts: msm:
Update sdhc_2 settings for QCS405") qcs405-pinctrl change,
which involved mute button does not work issue. Will raise
wlan_en related changes for sdio wlan later after gpio
conflict is resolved.

Change-Id: Ic7983c0a8510ff5abc1eb33572204cf54364d093
CRs-Fixed: 2522568
Signed-off-by: Hangtian Zhu <hangtian@codeaurora.org>