avcodec/cfhd: Fix decoding regression due to height check

Fixes: Ticket6546

Regression since: 54aaadf6

Reviewed-by: Muhammad Faiz <mfcc64@gmail.com>
Reviewed-by: Kieran Kunhya <kierank@obe.tv>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>