x86: Unconfuse CONFIG_ and X86_FEATURE_ namespaces

Lukas reported someone fat fingered the CONFIG_ symbol; fix er up.

Fixes: 5d821386 ("x86/retbleed: Add SKL return thunk")
Reported-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/Y1+fL4qQEIGZEEKB@hirez.programming.kicks-ass.net

arch/x86/include/asm/nospec-branch.h

@@ -285,7 +285,7 @@
  */
 .macro UNTRAIN_RET
 #if defined(CONFIG_CPU_UNRET_ENTRY) || defined(CONFIG_CPU_IBPB_ENTRY) || \
-	defined(CONFIG_X86_FEATURE_CALL_DEPTH)
+	defined(CONFIG_CALL_DEPTH_TRACKING)
 	ANNOTATE_UNRET_END
 	ALTERNATIVE_3 "",						\
 		      CALL_ZEN_UNTRAIN_RET, X86_FEATURE_UNRET,		\
@@ -296,7 +296,7 @@
 
 .macro UNTRAIN_RET_FROM_CALL
 #if defined(CONFIG_CPU_UNRET_ENTRY) || defined(CONFIG_CPU_IBPB_ENTRY) || \
-	defined(CONFIG_X86_FEATURE_CALL_DEPTH)
+	defined(CONFIG_CALL_DEPTH_TRACKING)
 	ANNOTATE_UNRET_END
 	ALTERNATIVE_3 "",						\
 		      CALL_ZEN_UNTRAIN_RET, X86_FEATURE_UNRET,		\