usb: xhci-msm-hsic: Fix bug in mxhci_hsic_ulpi_write()

GUSB2PHYACC_VSTSDONE register clears when ulpi phy write
request is initiated. mxhci_hsic_ulpi_write() needs to poll
for GUSB2PHYACC_VSTSDONE to get set instead of clear to finish
successful phy write operation.

Change-Id: I93c78ecfe5938e03a19dd8bc50da81b55926239a
Signed-off-by: Hemant Kumar <hemantk@codeaurora.org>