usb: phy: msm: Add support for secondary PHYs

The secondary HS- and SS-PHYs are architecturally dependent
on the primary PHYs, and thus need to be given special treatment
to not perform certain sequences that the primary is already
handling, such as initialization and reset. This can be simply
described by adding a device tree parameter that specifies the
phandle to the primary PHY.

Change-Id: Ib6bb8b1cc9e5b42485137536de1d07b17cdfc4fd
Signed-off-by: Jack Pham <jackp@codeaurora.org>