x86inc: Simplify AUTO_REP_RET

cpuflags is never undefined any more, it's set to 0 instead.

Also fix an incorrect comment.
Signed-off-by: NAnton Khirnov <anton@khirnov.net>

libavutil/x86/x86inc.asm

@@ -638,10 +638,8 @@ DECLARE_ARG 7, 8, 9, 10, 11, 12, 13, 14
 
 %define last_branch_adr $$
 %macro AUTO_REP_RET 0
-    %ifndef cpuflags
-        times ((last_branch_adr-$)>>31)+1 rep ; times 1 iff $ != last_branch_adr.
-    %elif notcpuflag(ssse3)
-        times ((last_branch_adr-$)>>31)+1 rep
+    %if notcpuflag(ssse3)
+        times ((last_branch_adr-$)>>31)+1 rep ; times 1 iff $ == last_branch_adr.
     %endif
     ret
 %endmacro