ANDROID: bpf: fix export symbol type

In commit ff5bf35998cc ("ANDROID: bpf: validate bpf_func when BPF_JIT is
enabled with CFI") a new symbol was exported, but it should have been
set as a _GPL symbol.

Fix this up by properly.

Bug: 145210207
Cc: Sami Tolvanen <samitolvanen@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
Change-Id: I7239bb8e0ef329cd7eac6afcd06c341b17ea680b