s390/crc32-vx: use expoline for indirect branches

The return from the crc32_le_vgfm_16/crc32c_le_vgfm_16 and the
crc32_be_vgfm_16 functions are done with "br %r14". These are indirect
branches as well and need to use execute trampolines for CONFIG_EXPOLINE=y.

Cc: stable@vger.kernel.org # 4.16
Fixes: f19fbd5e ("s390: introduce execute-trampolines for branches")
Reviewed-by: Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/crypto/crc32be-vx.S

@@ -13,6 +13,7 @@
  */
 
 #include <linux/linkage.h>
+#include <asm/nospec-insn.h>
 #include <asm/vx-insn.h>
 
 /* Vector register range containing CRC-32 constants */
@@ -67,6 +68,8 @@
 
 .previous
 
+	GEN_BR_THUNK %r14
+
 .text
 /*
  * The CRC-32 function(s) use these calling conventions:
@@ -203,6 +206,6 @@ ENTRY(crc32_be_vgfm_16)
 
 .Ldone:
 	VLGVF	%r2,%v2,3
-	br	%r14
+	BR_EX	%r14
 
 .previous

arch/s390/crypto/crc32le-vx.S

@@ -14,6 +14,7 @@
  */
 
 #include <linux/linkage.h>
+#include <asm/nospec-insn.h>
 #include <asm/vx-insn.h>
 
 /* Vector register range containing CRC-32 constants */
@@ -76,6 +77,7 @@
 
 .previous
 
+	GEN_BR_THUNK %r14
 
 .text
 
@@ -264,6 +266,6 @@ crc32_le_vgfm_generic:
 
 .Ldone:
 	VLGVF	%r2,%v2,2
-	br	%r14
+	BR_EX	%r14
 
 .previous