bpf: Allow calls to arena functions while holding spinlocks

bpf: Allow calls to arena functions while holding spinlocks

The bpf_arena_*_pages() kfuncs can be called from sleepable contexts,
but the verifier still prevents BPF programs from calling them while
holding a spinlock. Amend the verifier to allow for BPF programs
calling arena page management functions while holding a lock.

Signed-off-by: Emil Tsalapatis <emil@etsalapatis.com>
Link: https://lore.kernel.org/r/20260106-arena-under-lock-v2-2-378e9eab3066@etsalapatis.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>