[POWERPC] Never panic when taking altivec exceptions from userspace

At the moment we rely on a cpu feature bit or a firmware property to
detect altivec. If we dont have either of these and the cpu does in fact
support altivec we can cause a panic from userspace.

It seems safer to always send a signal if we manage to get an 0xf20
exception from userspace.
Signed-off-by: NAnton Blanchard <anton@samba.org>
Signed-off-by: NPaul Mackerras <paulus@samba.org>

arch/powerpc/kernel/traps.c

@@ -900,14 +900,13 @@ void kernel_fp_unavailable_exception(struct pt_regs *regs)
 
 void altivec_unavailable_exception(struct pt_regs *regs)
 {
-#if !defined(CONFIG_ALTIVEC)
 	if (user_mode(regs)) {
 		/* A user program has executed an altivec instruction,
 		   but this kernel doesn't support altivec. */
 		_exception(SIGILL, regs, ILL_ILLOPC, regs->nip);
 		return;
 	}
-#endif
+
 	printk(KERN_EMERG "Unrecoverable VMX/Altivec Unavailable Exception "
 			"%lx at %lx\n", regs->trap, regs->nip);
 	die("Unrecoverable VMX/Altivec Unavailable Exception", regs, SIGABRT);