powernow-k6: Really enable auto-loading

Commit fa8031ae ('cpufreq: Add support
for x86 cpuinfo auto loading v4') added a device ID table to this
driver, but didn't declare it as the module device ID table.

Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Acked-by: Thomas Renninger <trenn@suse.de>
Acked-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>