x86, bpf: Cleanup the top of file header in bpf_jit_comp.c

Don't bother mentioning the file name as it is implied, and remove the
reference to internal BPF.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/20211119163215.971383-2-hch@lst.de