spec: update buildrequires
spec: update buildrequires

Target amt.h uses xxd.
In clean buildroot we would miss this dep.

Signed-off-by: Martin Styk <e8f07f5a3c30658c8dc45287b190392d5b0d5633@redhat.com>

schnoddelbotz/amtc,schnoddelbotz/amtc,schnoddelbotz/amtc,schnoddelbotz/amtc,schnoddelbotz/amtc