powerpc/64s: Move cpu_show_meltdown()

This landed in setup_64.c for no good reason other than we had nowhere
else to put it. Now that we have a security-related file, that is a
better place for it so move it.

Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/kernel/security.c

@@ -5,6 +5,8 @@
 // Copyright 2018, Michael Ellerman, IBM Corporation.
 
 #include <linux/kernel.h>
+#include <linux/device.h>
+
 #include <asm/security_features.h>
 
 
@@ -13,3 +15,12 @@ unsigned long powerpc_security_features __read_mostly = \
 	SEC_FTR_L1D_FLUSH_PR | \
 	SEC_FTR_BNDS_CHK_SPEC_BAR | \
 	SEC_FTR_FAVOUR_SECURITY;
+
+
+ssize_t cpu_show_meltdown(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	if (rfi_flush)
+		return sprintf(buf, "Mitigation: RFI Flush\n");
+
+	return sprintf(buf, "Vulnerable\n");
+}