apm821xx: switch to pending xhci-pci-renesas solution

apm821xx: switch to pending xhci-pci-renesas solution

This patch replaces most of the out-of-tree xhci firmware
loader for the particular xhci chip from Renesas on the
WNDR4700's PCB.

What remains is a check in xhci-pci main driver which
guards against a 10 second delay during boot of the WNDR4700.
This is because the xhci-pci will still try to bud-in, but it
doesn't do anything useful, if the firmware isn't loaded, but
waste time and fail eventually:

[  375.481868] xhci_hcd 0000:45:00.0: xHCI Host Controller
[  375.487149] xhci_hcd 0000:45:00.0: new USB bus registered, assigned bus number 1
[  385.494590] xhci_hcd 0000:45:00.0: can't setup: -110
[  385.499558] xhci_hcd 0000:45:00.0: USB bus 1 deregistered
[  385.504963] xhci_hcd 0000:45:00.0: init 0000:45:00.0 fail, -110
[  385.510889] xhci_hcd: probe of 0000:45:00.0 failed with error -110

Signed-off-by: Christian Lamparter <chunkeey@gmail.com>