usb: early: xhci-dbc: Use memcpy_and_pad()

Instead of zeroing some memory and then copying data in part or all of it,
use memcpy_and_pad().
This avoids writing some memory twice and should save a few cycles.

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Link: https://lore.kernel.org/r/b447a7e9778d3f9e6997eb9494f1687dc2d5d3bf.1675016180.git.christophe.jaillet@wanadoo.fr
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>