USB: phy: Disable phy_irq before processing LPM sequence

phy_irq may arrive any time when the micro-A cable is connected.
If the USB low power mode sequence is ongoing, it would turn off
the usb core clock before setting the in_lpm flag. Because in_lpm
flag is not set, async irq would not resume USB. In such race
condition, there is a chance to hit into unclocked access noc
error.
Disable the phy_irq before beginning of the LPM sequence and enable
is back again at the end of LPM after setting in_lpm flag.

Change-Id: Ia5e7291502be05be88bbe4ae4c5d0920c9665ca2
Signed-off-by: Sujeet Kumar <ksujeet@codeaurora.org>