iproute2: Remove libxtables from some tc variants

iproute2: Remove libxtables from some tc variants

This adds the new tc-bpf variant and removes libxtables dependency from
the tc-tiny variant. The tc-full variant stays like before and contains
everything.

This allows to use tc without libxtables.

The variants have the following sizes:
root@OpenWrt:/# ls -al /usr/libexec/tc-*
-rwxr-xr-x    1 root     root        282453 Mar  1 21:55 /usr/libexec/tc-bpf
-rwxr-xr-x    1 root     root        282533 Mar  1 21:55 /usr/libexec/tc-full
-rwxr-xr-x    1 root     root        266037 Mar  1 21:55 /usr/libexec/tc-tiny

They are linking the following shared libraries:
root@OpenWrt:/# ldd /usr/libexec/tc-tiny
        /lib/ld-musl-mips-sf.so.1 (0x77d6e000)
        libgcc_s.so.1 => /lib/libgcc_s.so.1 (0x77d4a000)
        libc.so => /lib/ld-musl-mips-sf.so.1 (0x77d6e000)
root@OpenWrt:/# ldd /usr/libexec/tc-bpf
        /lib/ld-musl-mips-sf.so.1 (0x77da6000)
        libbpf.so.0 => /usr/lib/libbpf.so.0 (0x77d60000)
        libelf.so.1 => /usr/lib/libelf.so.1 (0x77d3e000)
        libgcc_s.so.1 => /lib/libgcc_s.so.1 (0x77d1a000)
        libc.so => /lib/ld-musl-mips-sf.so.1 (0x77da6000)
        libz.so.1 => /usr/lib/libz.so.1 (0x77cf6000)
root@OpenWrt:/# ldd /usr/libexec/tc-full
        /lib/ld-musl-mips-sf.so.1 (0x77de8000)
        libbpf.so.0 => /usr/lib/libbpf.so.0 (0x77da2000)
        libelf.so.1 => /usr/lib/libelf.so.1 (0x77d80000)
        libxtables.so.12 => /usr/lib/libxtables.so.12 (0x77d66000)
        libgcc_s.so.1 => /lib/libgcc_s.so.1 (0x77d42000)
        libc.so => /lib/ld-musl-mips-sf.so.1 (0x77de8000)
        libz.so.1 => /usr/lib/libz.so.1 (0x77d1e000)

This is based on a patch from Tiago Gaspar.

Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>