procd: drop nand_upgrade_stage1 from sysupgrade_pre_upgrade hooks

Now we have all targets using platform_pre_upgrade (and calling
nand_do_upgrade directly) we don't need nand_upgrade_stage1 to be in
sysupgrade_pre_upgrade hooks anymore.

Signed-off-by: Rafał Miłecki <zajec5@gmail.com>

SVN-Revision: 47489

package/system/procd/files/nand.sh

@@ -322,7 +322,6 @@ nand_upgrade_stage1() {
 		exit 0
 	}
 }
-append sysupgrade_pre_upgrade nand_upgrade_stage1
 
 # Check if passed file is a valid one for NAND sysupgrade. Currently it accepts
 # 3 types of files: