Merge from stable/10, r259745:

Merge from stable/10, r259745:

drm: Lower priority of "EDID checksum is invalid" message

The priority goes from "error" to "debug".

Connectors are polled every 10 seconds. Reading EDID is part of this
polling. However, when an invalid EDID is returned, this error message
is logged. When using Newcons for instance, having a kernel message
every 10 seconds is getting annoying.

Now that it's a debug message, it'll be logged only if hw.dri.debug is
enabled. This fix console spamming for some users.

Tested by:	Larry Rosenman <ler@lerctr.org>
Approved by:	re (gjb)

git-svn-id: svn://svn.freebsd.org/base/releng/10.0@259755 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f