xhci: fix platform quirks overwrite regression in 4.7-rc1

xhci: fix platform quirks overwrite regression in 4.7-rc1

commit b1c127ae990b ("usb: host: xhci: plat: make use of new methods in
xhci_plat_priv") sets xhci->quirks before calling xhci_gen_setup(), which
will overwrite them.

Don't overwite the quirks, just add the new ones

Fixes: b1c127ae990b ("usb: host: xhci: plat: make use of new methods in xhci_plat_priv")
Reported-by: Yoshihiro Shimoda <[email protected]>
Cc: Felipe Balbi <[email protected]>
Signed-off-by: Mathias Nyman <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>