objtool: Uniquely identify alternative instruction groups

Assign a unique identifier to every alternative instruction group in
order to be able to tell which instructions belong to what
alternative.

[peterz: extracted from a larger patch]
Signed-off-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
diff --git a/tools/objtool/check.h b/tools/objtool/check.h
index 12a9660..2428022 100644
--- a/tools/objtool/check.h
+++ b/tools/objtool/check.h
@@ -30,12 +30,13 @@ struct instruction {
 	unsigned int len;
 	enum insn_type type;
 	unsigned long immediate;
-	bool alt_group, dead_end, ignore, ignore_alts;
+	bool dead_end, ignore, ignore_alts;
 	bool hint;
 	bool retpoline_safe;
 	s8 instr;
 	u8 visited;
 	u8 ret_offset;
+	int alt_group;
 	struct symbol *call_dest;
 	struct instruction *jump_dest;
 	struct instruction *first_jump_src;