s390: disable asm code expolines if cc does not support it

To avoid a mixture of asm code with expolines and c code without them,
propagate CC_USING_EXPOLINE to KBUILD_AFLAGS and use it to detect
whether asm code should have expolines or not.
Reviewed-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/Makefile

@@ -82,6 +82,7 @@ ifdef CONFIG_EXPOLINE
     CC_FLAGS_EXPOLINE += -mindirect-branch-table
     export CC_FLAGS_EXPOLINE
     cflags-y += $(CC_FLAGS_EXPOLINE) -DCC_USING_EXPOLINE
+    aflags-y += -DCC_USING_EXPOLINE
   endif
 endif
 

arch/s390/include/asm/nospec-insn.h

@@ -8,7 +8,7 @@
 
 #ifdef __ASSEMBLY__
 
-#ifdef CONFIG_EXPOLINE
+#ifdef CC_USING_EXPOLINE
 
 _LC_BR_R1 = __LC_BR_R1
 
@@ -189,7 +189,7 @@ _LC_BR_R1 = __LC_BR_R1
 	.macro BASR_EX rsave,rtarget,ruse=%r1
 	basr	\rsave,\rtarget
 	.endm
-#endif
+#endif /* CC_USING_EXPOLINE */
 
 #endif /* __ASSEMBLY__ */