avr32: wire up copy_file_range syscall

This patch wires up the new copy_file_range syscall on AVR32.

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.
Signed-off-by: Hans-Christian Noren Egtvedt <egtvedt@samfundet.no>

arch/avr32/include/uapi/asm/unistd.h

@@ -337,5 +337,6 @@
 #define __NR_userfaultfd	322
 #define __NR_membarrier		323
 #define __NR_mlock2		324
+#define __NR_copy_file_range    325
 
 #endif /* _UAPI__ASM_AVR32_UNISTD_H */

arch/avr32/kernel/syscall-stubs.S

@@ -124,3 +124,12 @@ __sys_process_vm_writev:
 	call	sys_process_vm_writev
 	sub	sp, -4
 	popm	pc
+
+	.global __sys_copy_file_range
+	.type	__sys_copy_file_range,@function
+__sys_copy_file_range:
+	pushm	lr
+	st.w	--sp, ARG6
+	call	sys_copy_file_range
+	sub	sp, -4
+	popm	pc

arch/avr32/kernel/syscall_table.S

@@ -338,4 +338,5 @@ sys_call_table:
 	.long	sys_userfaultfd
 	.long	sys_membarrier
 	.long	sys_mlock2
+	.long   __sys_copy_file_range   /* 325 */
 	.long	sys_ni_syscall		/* r8 is saturated at nr_syscalls */