usb: phy: qmp: updated SIGDET_CNTRL value

The default value for RX_SIGDET_CNTRL register specified
in HPG (0x70) leads to LFPS detection issues by QMP PHY leading
to USB enumeration failures. Fixes to new value (0x73).

Change-Id: I742b5942deca7dc1d2c232c624d40efa3ed9e9b0
CRs-Fixed: 612380
Signed-off-by: Dov Levenglick <dovl@codeaurora.org>