powerpc/64: Make meltdown reporting Book3S 64 specific

In a subsequent patch we will enable building security.c for Book3E.
However the NXP platforms are not vulnerable to Meltdown, so make the
Meltdown vulnerability reporting PPC_BOOK3S_64 specific.

Signed-off-by: Diana Craciun <[e-mail]>
[mpe: Split out of larger patch]
Signed-off-by: Michael Ellerman <[e-mail]>

arch/powerpc/kernel/security.c

···
 device_initcall(barrier_nospec_debugfs_init);
 #endif /* CONFIG_DEBUG_FS */
 
+#ifdef CONFIG_PPC_BOOK3S_64
 ssize_t cpu_show_meltdown(struct device *dev, struct device_attribute *attr, char *buf)
 {
 	bool thread_priv;
···
 
 	return sprintf(buf, "Vulnerable\n");
 }
+#endif
 
 ssize_t cpu_show_spectre_v1(struct device *dev, struct device_attribute *attr, char *buf)
 {