phy: phy-rcar-gen2: Fix USBHS_UGSTS_LOCK value

According to the technical update (No. TN-RCS-B011A/E), the UGSTS LOCK
bit location is bit 8, not bits 1 and 0. It also says that the register
address offset of UGSTS is 0x88, not 0x90.
So, this patch fixes the USBHS_UGSTS_LOCK value and some comments.

Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>