drm/radeon: fix LCD record parsing

commit 95663948 upstream.

If the LCD table contains an EDID record, properly account
for the edid size when walking through the records.

This should fix error messages about unknown LCD records.

Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>