USB: EHCI: Add support for TCXO vote/unvote

PHY of HSUSB Core3 and Core4 takes TCXO reference clock as
XO input to run internal PHY clock at 60Mhz. Hence vote for
TCXO for the correct operation of the phy in active mode and
unvote only when PHY is in low power mode.

Change-Id: If474207ad3d07847d451e1eecbc57f8ef21d2ce5
CRs-Fixed: 356371
Signed-off-by: Hemant Kumar <hemantk@codeaurora.org>