kernel: mips: restore missing MIPS32 cBPF JIT

kernel: mips: restore missing MIPS32 cBPF JIT

Kernel v5.1 included an eBPF JIT for MIPS32 kernels, but problems were
discovered [1] and the changes later reverted in kernel v5.5 with commits:

  * f8fffebdea75 ("MIPS: BPF: Disable MIPS32 eBPF JIT")
  * 36366e367ee9 ("MIPS: BPF: Restore MIPS32 cBPF JIT")

Only the first of these was backported to LTS kernel 5.4, leaving cBPF
programs without a JIT and introducing a performance regression for any
such users e.g. libpcap, tcpdump, etc.

Restore cBPF performance by backporting the second commit above:
  * 070-v5.5-MIPS-BPF-Restore-MIPS32-cBPF-JIT.patch

[1] https://lore.kernel.org/bpf/20191205182318.2761605-1-paulburton@kernel.org/

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