[POWERPC] Declare enable_kernel_spe in a header

This patch puts enable_kernel_spe into <asm-powerpc/system.h> along with
enable_kernel_altivec etc.
Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: Paul Mackerras <paulus@samba.org>

include/asm-powerpc/system.h

@@ -131,6 +131,7 @@ extern void enable_kernel_altivec(void);
 extern void giveup_altivec(struct task_struct *);
 extern void load_up_altivec(struct task_struct *);
 extern int emulate_altivec(struct pt_regs *);
+extern void enable_kernel_spe(void);
 extern void giveup_spe(struct task_struct *);
 extern void load_up_spe(struct task_struct *);
 extern int fix_alignment(struct pt_regs *);