bpf: Convert lpm_trie.c to rqspinlock

Convert all LPM trie usage of raw_spinlock to rqspinlock.

Note that rcu_dereference_protected in trie_delete_elem is switched over
to plain rcu_dereference, the RCU read lock should be held from BPF
program side or eBPF syscall path, and the trie->lock is just acquired
before the dereference. It is not clear the reason the protected variant
was used from the commit history, but the above reasoning makes sense so
switch over.

Closes: https://lore.kernel.org/lkml/000000000000adb08b061413919e@google.com


Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20250316040541.108729-22-memxor@gmail.com


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