riscv, bpf: Use bpf_prog_pack for RV64 bpf trampoline

We used bpf_prog_pack to aggregate bpf programs into huge page to
relieve the iTLB pressure on the system. We can apply it to bpf
trampoline, as Song had been implemented it in core and x86 [0]. This
patch is going to use bpf_prog_pack to RV64 bpf trampoline. Since Song
and Puranjay have done a lot of work for bpf_prog_pack on RV64,
implementing this function will be easy.

Signed-off-by: Pu Lehui <pulehui@huawei.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Tested-by: Björn Töpel <bjorn@rivosinc.com> #riscv
Link: https://lore.kernel.org/all/20231206224054.492250-1-song@kernel.org [0]
Link: https://lore.kernel.org/bpf/20240622030437.3973492-4-pulehui@huaweicloud.com