avr32: fix sys_sync_file_range() call convention

On AVR32, all parameters beyond the 5th are passed on the stack. System
calls don't use the stack -- they borrow a callee-saved register
instead. This means that syscalls that take 6 parameters must be called
through a stub that pushes the last parameter on the stack.

This patch adds a stub for sync_file_range syscall on AVR32
architecture.  Tested with uClibc snapshot.
Signed-off-by: NHans-Christian Egtvedt <hans-christian.egtvedt@atmel.com>
Signed-off-by: NHaavard Skinnemoen <haavard.skinnemoen@atmel.com>

arch/avr32/kernel/syscall-stubs.S

@@ -109,3 +109,12 @@ __sys_epoll_pwait:
 	rcall	sys_epoll_pwait
 	sub	sp, -4
 	popm	pc
+
+	.global __sys_sync_file_range
+	.type	__sys_sync_file_range,@function
+__sys_sync_file_range:
+	pushm	lr
+	st.w	--sp, ARG6
+	rcall	sys_sync_file_range
+	sub	sp, -4
+	popm	pc

arch/avr32/kernel/syscall_table.S

@@ -275,7 +275,7 @@ sys_call_table:
 	.long	sys_set_robust_list
 	.long	sys_get_robust_list	/* 260 */
 	.long	__sys_splice
-	.long	sys_sync_file_range
+	.long	__sys_sync_file_range
 	.long	sys_tee
 	.long	sys_vmsplice
 	.long	__sys_epoll_pwait	/* 265 */