signal/powerpc: Call force_sig_fault from _exception

The callers of _exception don't need the pkey exception logic because
they are not processing a pkey exception.  So just call exception_common
directly and then call force_sig_fault to generate the appropriate siginfo
and deliver the appropriate signal.
Reviewed-by: NStephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: N"Eric W. Biederman" <ebiederm@xmission.com>

arch/powerpc/kernel/traps.c

@@ -380,7 +380,10 @@ void _exception_pkey(int signr, struct pt_regs *regs, int code, unsigned long ad
 
 void _exception(int signr, struct pt_regs *regs, int code, unsigned long addr)
 {
-	_exception_pkey(signr, regs, code, addr, 0);
+	if (!exception_common(signr, regs, code, addr))
+		return;
+
+	force_sig_fault(signr, code, (void __user *)addr, current);
 }
 
 void system_reset_exception(struct pt_regs *regs)