ptp: ocp: remove flash image header check fallback

Previously there was a fallback mode to flash firmware image without
proper header. But now we have different supported vendors and flashing
wrong image could destroy the hardware. Remove fallback mode and force
header check. Both vendors have published firmware images with headers.

Acked-by: Jonathan Lemon <jonathan.lemon@gmail.com>
Signed-off-by: Vadim Fedorenko <vadfed@fb.com>
Signed-off-by: David S. Miller <davem@davemloft.net>