powerpc: make facility_unavailable_exception 64s

The facility unavailable exception is only available on ppc book3s
machines so use CONFIG_PPC_BOOK3S_64 rather than CONFIG_PPC64.
tm_unavailable is only called from facility_unavailable_exception so can
also be under this Kconfig symbol.

Signed-off-by: Rashmica Gupta <[e-mail]>
Signed-off-by: Michael Ellerman <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

arch/powerpc/kernel/traps.c

···
 	die("Unrecoverable VSX Unavailable Exception", regs, SIGABRT);
 }
 
-#ifdef CONFIG_PPC64
+#ifdef CONFIG_PPC_BOOK3S_64
 static void tm_unavailable(struct pt_regs *regs)
 {
 #ifdef CONFIG_PPC_TRANSACTIONAL_MEM