usb: early: xhci-dbc: Remove duplicate keep parsing

The generic earlyprintk= parsing already parses the optional ",keep",
no need to duplicate that in the xdbc driver.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20220304152135.975568860@infradead.org


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>