Merge branch 'Allow BPF TCP CCs to write app_limited'

Yixin Shen says:

====================

This series allow BPF TCP CCs to write app_limited of struct
tcp_sock. A built-in CC or one from a kernel module is already
able to write to app_limited of struct tcp_sock. Until now,
a BPF CC doesn't have write access to this member of struct
tcp_sock.

v2:
 - Merge the test of writing app_limited into the test of
   writing sk_pacing. (Martin KaFai Lau)
====================

Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>