phy: sun4i-usb: Align H6 initialization logic with the kernel

H6 SOC needs additional initialization of PHY registers. Corresponding
changes can be found in the kernel patch [1].

Without this changes there is no enumeration of 'musb' gadget.

[1] - https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=ae409cc7c3cdb9ac4a1dba3eae70efec3d6b6c79



Fixes: 35fa673e ("sunxi: phy: Add USB PHY support for Allwinner H6")
Signed-off-by: Roman Stratiienko <r.stratiienko@gmail.com>
Reviewed-by: Jagan Teki <jagan@amarulasolutions.com>