drm/radeon: Don't destroy I2C Bus Rec in radeon_ext_tmds_enc_destroy().

radeon_i2c_fini() walks thru the list of I2C bus recs rdev->i2c_bus[]
to destroy each of them.
radeon_ext_tmds_enc_destroy() however also has code to destroy it's
associated I2C bus rec which has been obtained by radeon_i2c_lookup()
and is therefore also in the i2c_bus[] list.
This causes a double free resulting in a kernel panic when unloading
the radeon driver.
Removing destroy code from radeon_ext_tmds_enc_destroy() fixes this
problem.

agd5f: fix compiler warning
Signed-off-by: Egbert Eich <eich@suse.de>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org

drivers/gpu/drm/radeon/radeon_legacy_encoders.c

@@ -991,11 +991,7 @@ static void radeon_legacy_tmds_ext_mode_set(struct drm_encoder *encoder,
 static void radeon_ext_tmds_enc_destroy(struct drm_encoder *encoder)
 {
 	struct radeon_encoder *radeon_encoder = to_radeon_encoder(encoder);
-	struct radeon_encoder_ext_tmds *tmds = radeon_encoder->enc_priv;
-	if (tmds) {
-		if (tmds->i2c_bus)
-			radeon_i2c_destroy(tmds->i2c_bus);
-	}
+	/* don't destroy the i2c bus record here, this will be done in radeon_i2c_fini */
 	kfree(radeon_encoder->enc_priv);
 	drm_encoder_cleanup(encoder);
 	kfree(radeon_encoder);