[S390] fix s390 assembler code alignments

The alignment is missing for various global symbols in s390 assembly code.
With a recent gcc and an instruction like stgrl this can lead to a
specification exception if the instruction uses such a mis-aligned address.

Specify the alignment explicitely and while add it define __ALIGN for s390
and use the ENTRY define to save some lines of code.

Signed-off-by: Jan Glauber <jang@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/kernel/head64.S

@@ -11,13 +11,13 @@
  */
 
 #include <linux/init.h>
+#include <linux/linkage.h>
 #include <asm/asm-offsets.h>
 #include <asm/thread_info.h>
 #include <asm/page.h>
 
 __HEAD
-	.globl	startup_continue
-startup_continue:
+ENTRY(startup_continue)
 	larl	%r1,sched_clock_base_cc
 	mvc	0(8,%r1),__LC_LAST_UPDATE_CLOCK
 	larl	%r13,.LPG1		# get base
@@ -76,8 +76,7 @@ startup_continue:
 	.long	0x80000000,0,0,0	# invalid access-list entries
 	.endr
 
-	.globl	_ehead
-_ehead:
+ENTRY(_ehead)
 
 #ifdef CONFIG_SHARED_KERNEL
 	.org	0x100000 - 0x11000	# head.o ends at 0x11000
@@ -86,8 +85,8 @@ _ehead:
 #
 # startup-code, running in absolute addressing mode
 #
-	.globl	_stext
-_stext:	basr	%r13,0			# get base
+ENTRY(_stext)
+	basr	%r13,0			# get base
 .LPG3:
 # check control registers
 	stctg	%c0,%c15,0(%r15)