acer-wmi: make dmi_matched to return 1 instead of 0

dmi_check_system() walks the table running matching functions until someone
returns non zero or we hit the end.

This patch makes dmi_matched to return 1 so dmi_check_system() return
immediately when a match is found.

Signed-off-by: Axel Lin <axel.lin@gmail.com>
Signed-off-by: Matthew Garrett <mjg@redhat.com>