arch: arm: mach-snapdragon: Auto-detect USB SSPHY driver support

arch: arm: mach-snapdragon: Auto-detect USB SSPHY driver support

Automatically detect super-speed USB PHY driver availability and
skip the USB speed fixup if driver is available, eliminating the need
for manual configuration.

Previously, U-Boot unconditionally limited USB to high-speed mode
on all Qualcomm platforms because most lacked super-speed PHY
drivers.

This change implements runtime detection that checks if a PHY
driver exists for the super-speed PHY node referenced by the DWC3
controller. The fixup is automatically skipped when a compatible
driver is found, allowing the hardware to operate at full
capability. Platforms without super-speed PHY drivers continue to
receive the fixup automatically.

Signed-off-by: Balaji Selvanathan <balaji.selvanathan@oss.qualcomm.com>
[casey: rebased on flat-dwc3 dt support + fix Balaji's signoff]
[casey: make erroneous printf() a debug() again]
Link: https://patch.msgid.link/20251203110735.1959862-5-balaji.selvanathan@oss.qualcomm.com
Signed-off-by: Casey Connolly <casey.connolly@linaro.org>