parisc: fix `struct pt_regs' declared inside parameter list warning

Fix those compile warnings:
uaccess.h:244: warning: `struct pt_regs' declared inside parameter list
uaccess.h:244: warning: its scope is only this definition or declaration, which is probably not what you want

Signed-off-by: Helge Deller <deller@gmx.de>
Signed-off-by: Kyle McMartin <kyle@mcmartin.ca>