usb: phy: Add BIAS_CTRL2 register offset as mandatory

BIAS_CTRL2 register is required to be override by QUSB PHY in
some cases. Hence add BIAS_CTRL2 register offset with QUSB PHY
device node on SDM845, and also modify check for to make sure
that all mandatory register offsets are provided.

Change-Id: I845a5a1dd6498a651f77eeab4b146395cfec7336
Signed-off-by: Mayank Rana <mrana@codeaurora.org>