usb: dwc3-msm: Remove use of QSCRATCH_CTRL_REG

QSCRATCH_CTRL_REG was used to restore the POR value after
userspace was done with charger detection. Since on newer platforms
charger detection is handled by dedicated charging hardware, hence
userapce charging is not needed. So remove this dead code.

Change-Id: Ie2baa1855315d044653d338ea2cf8a31efc8f08a
Signed-off-by: Azhar Shaikh <azhars@codeaurora.org>