drm/edid: fix a debug message

There is an extra semi-colon on the if statement so the debug output
always says "Failed to write EDID checksum" even when it didn't fail.

Fixes: 559be30c

 ('drm/i915: Implement the intel_dp_autotest_edid function for DP EDID complaince tests')
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>