MAINTAINERS: Add BPF JIT for LOONGARCH entry

After commit 5dc61552 ("LoongArch: Add BPF JIT support"),
there is no BPF JIT for LOONGARCH entry, in order to maintain
the current code and the new features timely, just add it.

Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>