src/lib/edid.c: missing break statement

While vendor specific extension blocks are mostly opaque to us,
they're not exactly "unknown".

Change-Id: I9136c04d12045ad13ef4f942c0814c4df88bdf6b
Found-by: Coverity Scan
Signed-off-by: Patrick Georgi <patrick@georgi-clan.de>
Reviewed-on: http://review.coreboot.org/6563
Reviewed-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>
Tested-by: build bot (Jenkins)
Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>
1 file changed