bpf, scripts: Correct GPL license name

The bpf_doc script refers to the GPL as the "GNU Privacy License".
I strongly suspect that the author wanted to refer to the GNU General
Public License, under which the Linux kernel is released, as, to the
best of my knowledge, there is no license named "GNU Privacy License".
This patch corrects the license name in the script accordingly.

Fixes: 56a092c89505 ("bpf: add script and prepare bpf.h for new helpers documentation")
Signed-off-by: Gianmarco Lusvardi <[e-mail]>
Signed-off-by: Daniel Borkmann <[e-mail]>
Reviewed-by: Quentin Monnet <[e-mail]>
Link: https://lore.kernel.org/bpf/[e-mail]

scripts/bpf_doc.py

···
 instructions to the kernel when the programs are loaded. The format for that
 string is identical to the one in use for kernel modules (Dual licenses, such
 as "Dual BSD/GPL", may be used). Some helper functions are only accessible to
-programs that are compatible with the GNU Privacy License (GPL).
+programs that are compatible with the GNU General Public License (GNU GPL).
 
 In order to use such helpers, the eBPF program must be loaded with the correct
 license string passed (via **attr**) to the **bpf**\\ () system call, and this