usb: dwc3-msm: Add soft dependency on phy drivers

dwc3-msm driver is functionally dependent on the phy-generic,
phy-msm-snps-hs, and phy-msm-ssusb-qmp drivers. Hence, explicitly
add a soft-dependency on it to avoid unnecessary re-probes
when built as a module.

Change-Id: I16d3a3fb72a968b0ae7935df74cff86697a97c32
Signed-off-by: Raghavendra Rao Ananta <rananta@codeaurora.org>