arm64: entry32: remove pointless register assignment

We currently set x27 in compat_sys_sigreturn_wrapper and
compat_sys_rt_sigreturn_wrapper, similarly to what we do with r8/why on
32-bit ARM, in an attempt to prevent sigreturns from being restarted.

However, on arm64 we have always used pt_regs::syscallno for syscall
restarting (for both native and compat tasks), and x27 is never
inspected again before being overwritten in kernel_exit.

This patch removes the pointless register assignments.
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

arch/arm64/kernel/entry32.S

@@ -32,13 +32,11 @@
 
 ENTRY(compat_sys_sigreturn_wrapper)
 	mov	x0, sp
-	mov	x27, #0		// prevent syscall restart handling (why)
 	b	compat_sys_sigreturn
 ENDPROC(compat_sys_sigreturn_wrapper)
 
 ENTRY(compat_sys_rt_sigreturn_wrapper)
 	mov	x0, sp
-	mov	x27, #0		// prevent syscall restart handling (why)
 	b	compat_sys_rt_sigreturn
 ENDPROC(compat_sys_rt_sigreturn_wrapper)