sysdata: Set fixed part for environment location

Loading the part doesn't work at the moment. Use a fixed part of 0.

sysdata/mmc.c

@@ -21,7 +21,8 @@
 static unsigned char env_mmc_orig_hwpart;
 
 static int mmc_set_sysdata_part( struct mmc *mmc ) {
-	uint part = mmc_get_env_part( mmc );
+	/*uint part = mmc_get_env_part( mmc );*/
+	uint part = 0;
 	int dev = mmc_get_env_dev( );
 	int ret = 0;