[S390] empty function defines.

Use do { } while (0) constructs instead of empty defines to avoid
subtle compile bugs.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
diff --git a/include/asm-s390/dma.h b/include/asm-s390/dma.h
index 02720c4..7425c6a 100644
--- a/include/asm-s390/dma.h
+++ b/include/asm-s390/dma.h
@@ -11,6 +11,6 @@
 
 #define MAX_DMA_ADDRESS         0x80000000
 
-#define free_dma(x)
+#define free_dma(x)	do { } while (0)
 
 #endif /* _ASM_DMA_H */
diff --git a/include/asm-s390/io.h b/include/asm-s390/io.h
index d4614b3..a6cc27e 100644
--- a/include/asm-s390/io.h
+++ b/include/asm-s390/io.h
@@ -116,7 +116,7 @@
 #define outb(x,addr) ((void) writeb(x,addr))
 #define outb_p(x,addr) outb(x,addr)
 
-#define mmiowb()
+#define mmiowb()	do { } while (0)
 
 /*
  * Convert a physical pointer to a virtual kernel pointer for /dev/mem
diff --git a/include/asm-s390/smp.h b/include/asm-s390/smp.h
index 6576460..9fb02e9 100644
--- a/include/asm-s390/smp.h
+++ b/include/asm-s390/smp.h
@@ -104,7 +104,7 @@
 #define smp_cpu_not_running(cpu)	1
 #define smp_get_cpu(cpu) ({ 0; })
 #define smp_put_cpu(cpu) ({ 0; })
-#define smp_setup_cpu_possible_map()
+#define smp_setup_cpu_possible_map()	do { } while (0)
 #endif
 
 #endif