Revert "usb: xhci: Raspberry Pi FW loader for VIA VL805"

This reverts commit 57edd519.

With [1] and [2] upstream, this downstream implementation is unneeded,
to the point that it breaks USB support on a rev 1.4 Pi 4.

[1] fbbc5ff3 ("firmware: raspberrypi: Introduce vl805 init routine")
[2] 65822fef4adc ("USB: pci-quirks: Add Raspberry Pi 4 quirk")

See: https://github.com/raspberrypi/linux/issues/3747



Signed-off-by: Phil Elwell <phil@raspberrypi.com>