bpf, core: Fix kernel-doc notation

Fix kernel-doc warnings in kernel/bpf/core.c (found by scripts/kernel-doc
and W=1 builds). That is, correct a function name in a comment and add
return descriptions for 2 functions.

Fixes these kernel-doc warnings:

  kernel/bpf/core.c:1372: warning: expecting prototype for __bpf_prog_run(). Prototype was for ___bpf_prog_run() instead
  kernel/bpf/core.c:1372: warning: No description found for return value of '___bpf_prog_run'
  kernel/bpf/core.c:1883: warning: No description found for return value of 'bpf_prog_select_runtime'
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20210809215229.7556-1-rdunlap@infradead.org

kernel/bpf/core.c

@@ -1362,11 +1362,13 @@ u64 __weak bpf_probe_read_kernel(void *dst, u32 size, const void *unsafe_ptr)
 }
 
 /**
- *	__bpf_prog_run - run eBPF program on a given context
+ *	___bpf_prog_run - run eBPF program on a given context
  *	@regs: is the array of MAX_BPF_EXT_REG eBPF pseudo-registers
  *	@insn: is the array of eBPF instructions
  *
  * Decode and execute eBPF instructions.
+ *
+ * Return: whatever value is in %BPF_R0 at program exit
  */
 static u64 ___bpf_prog_run(u64 *regs, const struct bpf_insn *insn)
 {
@@ -1878,6 +1880,9 @@ static void bpf_prog_select_func(struct bpf_prog *fp)
  *
  * Try to JIT eBPF program, if JIT is not available, use interpreter.
  * The BPF program will be executed via BPF_PROG_RUN() macro.
+ *
+ * Return: the &fp argument along with &err set to 0 for success or
+ * a negative errno code on failure
  */
 struct bpf_prog *bpf_prog_select_runtime(struct bpf_prog *fp, int *err)
 {