usb: early: xhci-dbc: Fix xdbc number parsing

kstrtoul() assumes the string contains the number only and is \0
terminated, this is not the case, as such things like:

	earlyprintk=xdbc1,keep

go completely sideways. Use simple_strtoul() instead.

Acked-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20220304152136.035911620@infradead.org


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