parisc: remove duplicated #include

Remove duplicated #include('s) in
  arch/parisc/kernel/signal.c

Signed-off-by: Huang Weiyi <weiyi.huang@gmail.com>
Signed-off-by: Kyle McMartin <kyle@mcmartin.ca>

arch/parisc/kernel/signal.c

@@ -26,7 +26,6 @@
 #include <linux/stddef.h>
 #include <linux/compat.h>
 #include <linux/elf.h>
-#include <linux/tracehook.h>
 #include <asm/ucontext.h>
 #include <asm/rt_sigframe.h>
 #include <asm/uaccess.h>