bpf: Use try_alloc_pages() to allocate pages for bpf needs.

Use try_alloc_pages() and free_pages_nolock() for BPF needs
when context doesn't allow using normal alloc_pages.
This is a prerequisite for further work.

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/r/20250222024427.30294-7-alexei.starovoitov@gmail.com


Signed-off-by: Alexei Starovoitov <ast@kernel.org>