arm/dts: 8974: Use corner voltages for VDDCX voting for HSIC

Currently hsic driver is voting for discrete voltages for VDDCX instead
of corner voltages. This could cause issue as RPM may not able to handle
this descrete voltage request for VDDCX on some platforms. Hence vote
for corner voltage for VDDCX instead of discrete voltages on new platforms.

Change-Id: I580b1fc84b94708acccc5b4e3b92511689a9889e
Signed-off-by: Vijayavardhan Vennapusa <vvreddy@codeaurora.org>