ARM: dts: msm: Add clock scaling entries for sdhc(1 & 2) on 8937

Add clock scaling frequencies for SDHC2 (SD card). This would
enable switching to lower frequencies in video playback
use-cases.
Modify the clock scaling frequencies for SDHC1 (eMMC).

Change-Id: I29b2641b10325285bd269be974ede161e3f1348b
Signed-off-by: Asutosh Das <asutoshd@codeaurora.org>
[riteshh@codeaurora.org: resolve trivial merge conflicts]
Signed-off-by: Ritesh Harjani <riteshh@codeaurora.org>