bcm53xx: drop target's preinit network support script

We don't need it anymore since the rework of generic preinit script.

Signed-off-by: Rafał Miłecki <[email protected]>

target/linux/bcm53xx/base-files/lib/preinit/05_set_preinit_iface_bcm53xx

@@ -1,7 +0,0 @@
-#!/bin/sh
-
-set_preinit_iface() {
-	ifname=eth0
-}
-
-boot_hook_add preinit_main set_preinit_iface