usb: xhci: dbc: Use GFP_KERNEL instead of GFP_ATOMIC in 'xhci_dbc_alloc_requests()'

There is no need to use GFP_ATOMIC to allocate 'req'. GFP_KERNEL should be
enough and is already used for another allocation juste a few lines below.

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Link: https://lore.kernel.org/r/1567172356-12915-3-git-send-email-mathias.nyman@linux.intel.com


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