MAINTAINERS: remove typo from XEN PVUSB DRIVER section

Commit a92548f9

 ("xen: add Xen pvUSB maintainer") adds the new XEN
PVUSB DRIVER section, but one file entry contains an obvious typo.

Fortunately, ./scripts/get_maintainer.pl --self-test=patterns warns:

  warning: no file matches    F:    divers/usb/host/xen*

Remove this obvious typo.

Reviewed-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Link: https://lore.kernel.org/r/20211216065547.18619-1-lukas.bulwahn@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>