base-files: ipcalc.sh: use shebang to invoke awk

There's hardly an shell logic in ipcalc.sh and a $* that would garble
parameter positions.
Move the awk invokation to the shebang.

A rename from "ipcalc.sh" to "ipcalc" is desirable but could prove tricky
with packages in other repositories depending on the filename.

Signed-off-by: Leon M. George <leon@georgemail.eu>

package/base-files/files/bin/ipcalc.sh

@@ -1,6 +1,5 @@
-#!/bin/sh
+#!/usr/bin/awk -f
 
-awk -f - $* <<EOF
 function bitcount(c) {
 	c=and(rshift(c, 1),0x55555555)+and(c,0x55555555)
 	c=and(rshift(c, 2),0x33333333)+and(c,0x33333333)
@@ -82,4 +81,3 @@ BEGIN {
 	print "START="int2ip(start)
 	print "END="int2ip(end)
 }
-EOF