s390: use proper expoline sections for .dma code

The text_dma.S code uses its own macro to generate an inline version of an
expoline. To make it easier to identify all expolines in the kernel use a
thunk and a branch to the thunk just like the rest of the kernel code does
it.

The name of the text_dma.S expoline thunk is __dma__s390_indirect_jump_r14
and the section is named .dma.text.__s390_indirect_jump_r14.

This will be needed for the objtool support.

Signed-off-by: Martin Schwidefsky <[e-mail]>

arch/s390/boot/text_dma.S

···
 #include <asm/errno.h>
 #include <asm/sigp.h>
 
+#ifdef CC_USING_EXPOLINE
+	.pushsection .dma.text.__s390_indirect_jump_r14,"axG"
+__dma__s390_indirect_jump_r14:
+	larl	%r1,0f
+	ex	0,0(%r1)
+	j	.
+0:	br	%r14
+	.popsection
+#endif
+
 	.section .dma.text,"ax"
 /*
  * Simplified version of expoline thunk. The normal thunks can not be used here,
···
  * affects a few functions that are not performance-relevant.
  */
 	.macro BR_EX_DMA_r14
-	larl	%r1,0f
-	ex	0,0(%r1)
-	j	.
-0:	br	%r14
+#ifdef CC_USING_EXPOLINE
+	jg	__dma__s390_indirect_jump_r14
+#else
+	br	%r14
+#endif
 	.endm
 
 /*