treewide: drop shebang from non-executable target files

This drops the shebang from all target files for /lib and
/etc/uci-defaults folders, as these are sourced and the shebang
is useless.

While at it, fix the executable flag on a few of these files.

This does not touch ar71xx, as this target is just used for
backporting now and applying cosmetic changes would just complicate
things.

Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>

target/linux/mediatek/base-files/lib/preinit/05_set_preinit_iface

@@ -1,5 +1,3 @@
-#!/bin/sh
-
 set_preinit_iface() {
 	ifconfig eth0 up
 	ifname=lan1

target/linux/mediatek/base-files/lib/preinit/06_set_rps_sock_flow

@@ -1,5 +1,3 @@
-#!/bin/sh
-
 set_rps_sock_flow() {
 	echo 1024 > /proc/sys/net/core/rps_sock_flow_entries
 }