usb: phy: qusb: Add wrapper function for phy reset

Currently the phy driver is asserting and deasserting
usb phy reset signal to reset qusb phy. This changes adds
a wrapper function around the assert and deassert of usb
phy reset signal to make the code more readable and remove
code duplicacy.

Change-Id: I4fa03ae2d6bccf7386fcf3a7aa5df0345054147d
Signed-off-by: Pratham Pratap <prathampratap@codeaurora.org>