USB: phy-msm-usb: Remove CORNER voting values

Rpm regulator header file is not moving to common
location and would not be supported further. This
is file mainly used on A family targets and newer
voting mechanism is via device tree. Hence fail
the probe if device tree entry does not exist.

Change-Id: Id25b51c98b84757079d0b0e25aa194b3e3191887
Signed-off-by: Sujeet Kumar <ksujeet@codeaurora.org>