drm: Fix doc warning in drm_connector_attach_edid_property()

Fixes the following warnings:
../drivers/gpu/drm/drm_connector.c:305: warning: Excess function parameter 'dev' description in 'drm_connector_attach_edid_property'
../drivers/gpu/drm/drm_connector.c:306: warning: Excess function parameter 'dev' description in 'drm_connector_attach_edid_property'
../drivers/gpu/drm/drm_connector.c:305: warning: Excess function parameter 'dev' description in 'drm_connector_attach_edid_property'
../drivers/gpu/drm/drm_connector.c:305: warning: Excess function parameter 'dev' description in 'drm_connector_attach_edid_property'
../drivers/gpu/drm/drm_connector.c:305: warning: Excess function parameter 'dev' description in 'drm_connector_attach_edid_property'

Fixes: 6b7e2d5c ("drm: add drm_connector_attach_edid_property()")
Cc: Gerd Hoffmann <kraxel@redhat.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: dri-devel@lists.freedesktop.org
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Sean Paul <seanpaul@chromium.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20181024182442.206411-1-sean@poorly.run