bpf: fix cbpf parser bug for octal numbers

Range is 0-7, not 0-9, otherwise parser silently excludes it from the
strtol() rather than throwing an error.

Reported-by: Marc Boschma <marc@boschma.cx>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

tools/bpf/bpf_exp.l

@@ -175,7 +175,7 @@ extern void yyerror(const char *str);
 			yylval.number = strtol(yytext, NULL, 10);
 			return number;
 		}
-([0][0-9]+)	{
+([0][0-7]+)	{
 			yylval.number = strtol(yytext + 1, NULL, 8);
 			return number;
 		}