bpf/docs: Update documentation for new cpumask kfuncs

bpf/docs: Update documentation for new cpumask kfuncs

We recently added the bpf_cpumask_first_and() kfunc, and changed
bpf_cpumask_any() / bpf_cpumask_any_and() to
bpf_cpumask_any_distribute() and bpf_cpumask_any_distribute_and()
respectively. This patch adds an entry for the bpf_cpumask_first_and()
kfunc, and updates the documentation for the *any* kfuncs to the new
names.

Signed-off-by: David Vernet <void@manifault.com>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/r/20230610035053.117605-5-void@manifault.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>