arm: fixed the ARM version of the routine __cr_restore_rt

This patch fixes a stack corruption caused by the routine
since it pushes the registers R4, R5, R6, and R7
onto the stack that results in a restorer crash
while restoring a zombie (https://bugzilla.openvz.org/show_bug.cgi?id=2663)
Reported-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Alexander Kartashov <alekskartashov@parallels.com>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

arch/arm/syscall-common.S

@@ -22,5 +22,7 @@ syscall_common:
 
 
 ENTRY(__cr_restore_rt)
-	b	sys_rt_sigreturn
+	adr	%r7, .nr_sys_rt_sigreturn
+	ldr	%r7, [%r7]
+	svc	#0
 END(__cr_restore_rt)