bpf, arm64: Remove redundant bpf_flush_icache() after pack allocator finalize

bpf, arm64: Remove redundant bpf_flush_icache() after pack allocator finalize

bpf_flush_icache() calls flush_icache_range() to clean the data cache
and invalidate the instruction cache for the JITed code region. However,
since commit 1dad391daef1 ("bpf, arm64: use bpf_prog_pack for memory
management"), this flush is redundant.

bpf_jit_binary_pack_finalize() copies the JITed instructions to the ROX
region via bpf_arch_text_copy() -> aarch64_insn_copy() -> __text_poke(),
and __text_poke() already calls flush_icache_range() on the written
range. The subsequent bpf_flush_icache() repeats the same cache
maintenance on an overlapping range, including an unnecessary second
synchronous IPI to all CPUs via kick_all_cpus_sync().

Remove the redundant bpf_flush_icache() call and its now-unused
definition.

Fixes: 1dad391daef1 ("bpf, arm64: use bpf_prog_pack for memory management")
Acked-by: Song Liu <song@kernel.org>
Signed-off-by: Puranjay Mohan <puranjay@kernel.org>
Acked-by: Breno Leitao <leitao@debian.org>
Link: https://lore.kernel.org/r/20260413191111.3426023-2-puranjay@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>