parisc: Drop parisc special case for __sighandler_t

I believe we can and *should* drop this parisc-specific typedef for __sighandler_t when compiling a 64-bit kernel. The reasons:

1. We don't have a 64-bit userspace yet, so nothing (on userspace side) can break.

2. Inside the Linux kernel, this is only used in kernel/signal.c, in function kernel_sigaction() where the signal handler is compared against SIG_IGN. SIG_IGN is defined as (__sighandler_t)1), so only the pointers are compared.

3. Even when a 64-bit userspace gets added at some point, I think __sighandler_t should be defined what it is: a function pointer struct.

I compiled kernel/signal.c with and without the patch, and the produced code is identical in both cases.

Opinions?
Do I miss something?
If we want to change it, we should do it before this patch gets applied:
https://patchwork.kernel.org/patch/11730893/

index e605197b462c..d9c51769851a 100644
@@ -85,16 +85,8 @@
 struct siginfo;
 
 /* Type of a signal handler.  */
-#if defined(__LP64__)
-/* function pointers on 64-bit parisc are pointers to little structs and the
- * compiler doesn't support code which changes or tests the address of
- * the function in the little struct.  This is really ugly -PB
- */
-typedef char __user *__sighandler_t;
-#else
 typedef void __signalfn_t(int);
 typedef __signalfn_t __user *__sighandler_t;
-#endif
 
 typedef struct sigaltstack {
 	void __user *ss_sp;