bpf: change int cmd argument in __sys_bpf into typed enum bpf_cmd

This improves BTF data recorded about this function and makes
debugging/tracing better, because now command can be displayed as
symbolic name, instead of obscure number.

Signed-off-by: Andrii Nakryiko <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Alexei Starovoitov <[e-mail]>

kernel/bpf/syscall.c

···
 	return bpf_token_create(attr);
 }
 
-static int __sys_bpf(int cmd, bpfptr_t uattr, unsigned int size)
+static int __sys_bpf(enum bpf_cmd cmd, bpfptr_t uattr, unsigned int size)
 {
 	union bpf_attr attr;
 	int err;