iproute2: update to 5.11.0

The latest iproute2 version brings various improvements and fixes:
https://git.kernel.org/pub/scm/network/iproute2/iproute2.git/log/?qt=range&q=v5.10.0..v5.11.0

In particular, ip and tc now use libbpf as the standard way to load BPF
programs, rather than the old, limited custom loader. This allows more
consistent and featureful BPF program handling e.g. support for global
initialized variables.

Also fix a longstanding problem with iproute2 builds where unneeded DSO
dependencies are added to most utilities, bloating their installation
footprint. From research and testing, explicitly using a "--as-needed"
linker flag avoids the issue. Update accordingly and drop extra package
dependencies from Makefile.

Additional build and packaging updates include:

  - install missing development header to iproute2/bpf_elf.h
  - propagate OpenWrt verbose flag during build
  - update and refresh patches

Compile and run tested: QEMU/malta-mips32be on kernels 5.4 & 5.10.

All iproute2 packages were built and installed to the test image. Some
regression testing using ip-full and tc was successfully performed to
exercise several kmods, tc modules, and simple BPF programs.

Signed-off-by: Tony Ambardar <itugrok@yahoo.com>

package/network/utils/iproute2/patches/300-selinux-configurable.patch

@@ -1,6 +1,6 @@
 --- a/configure
 +++ b/configure
-@@ -244,7 +244,7 @@ check_elf()
+@@ -354,7 +354,7 @@ check_libbpf()
  check_selinux()
  # SELinux is a compile time option in the ss utility
  {