USB: msm_otg: Rename MHL USB high speed switch regulator name

USB DP and DM lines are routed to USB PHY via MHL transmitter chip
if it is present on the board.  MHL transmitter route USB DP and DM
lines to MSM based on the High Speed Switch position.  The regulator
controlling this switch is different across targets.  For example
this switch is powered up by 3.3V regulator on 8960 Liquid and it is
5V regulator on 8930 fluid.  Hence rename existing "mhl_ext_3p3v"
supply name to a generic name "mhl_usb_hs_switch".

Change-Id: I35a6240fdbb01fa6b695a52968cd141d9418def7
Signed-off-by: Pavankumar Kondeti <pkondeti@codeaurora.org>