bpf: update the comment about the length of analysis

Commit 07016151a446 ("bpf, verifier: further improve search
pruning") increased the limit of processed instructions from
32k to 64k, but the comment still mentioned the 32k limit.
This commit updates the comment to reflect the change.

Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Gary Lin <glin@suse.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

kernel/bpf/verifier.c

@@ -33,7 +33,7 @@
  * - out of bounds or malformed jumps
  * The second pass is all possible path descent from the 1st insn.
  * Since it's analyzing all pathes through the program, the length of the
- * analysis is limited to 32k insn, which may be hit even if total number of
+ * analysis is limited to 64k insn, which may be hit even if total number of
  * insn is less then 4K, but there are too many branches that change stack/regs.
  * Number of 'branches to be analyzed' is limited to 1k
  *