bpf: Add bpf_jit_blinding_enabled for !CONFIG_BPF_JIT

Add a definition of bpf_jit_blinding_enabled() when CONFIG_BPF_JIT is not set
in order to fix a recent build regression:

  [...]
  CC      kernel/bpf/verifier.o
  CC      kernel/bpf/inode.o
kernel/bpf/verifier.c: In function ‘fixup_bpf_calls’:
kernel/bpf/verifier.c:9132:25: error: implicit declaration of function ‘bpf_jit_blinding_enabled’; did you mean ‘bpf_jit_kallsyms_enabled’? [-Werror=implicit-function-declaration]
 9132 |  bool expect_blinding = bpf_jit_blinding_enabled(prog);
      |                         ^~~~~~~~~~~~~~~~~~~~~~~~
      |                         bpf_jit_kallsyms_enabled
  CC      kernel/bpf/helpers.o
  CC      kernel/bpf/hashtab.o
  [...]

Fixes: d2e4c1e ("bpf: Constant map key tracking for prog array pokes")
Reported-by: Jakub Sitnicki <jakub@cloudflare.com>
Reported-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/40baf8f3507cac4851a310578edfb98ce73b5605.1574541375.git.daniel@iogearbox.net

include/linux/filter.h

@@ -1053,6 +1053,11 @@ static inline bool ebpf_jit_enabled(void)
 	return false;
 }
 
+static inline bool bpf_jit_blinding_enabled(struct bpf_prog *prog)
+{
+	return false;
+}
+
 static inline bool bpf_prog_ebpf_jited(const struct bpf_prog *fp)
 {
 	return false;