ARM: dts: msm: use Nominal/SVS2 freq for SDHC device for 8996

With this change, SDC will support scaling between these
frequencies:
1) Nominal (200Mhz)
2) SVS2 (20Mhz)

Change-Id: I4b484e37cd65bfb7af4067d93163af65cf4f944c
Signed-off-by: Talel Shenhar <tatias@codeaurora.org>