s390/mm: Remove sev_active() function

All references to sev_active() were moved to arch/x86 so we don't need to
define it for s390 anymore.

Signed-off-by: Thiago Jung Bauermann <bauerman@linux.ibm.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Halil Pasic <pasic@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20190806044919.10622-7-bauerman@linux.ibm.com

arch/s390/mm/init.c

@@ -156,14 +156,9 @@ int set_memory_decrypted(unsigned long addr, int numpages)
 }
 
 /* are we a protected virtualization guest? */
-bool sev_active(void)
-{
-	return is_prot_virt_guest();
-}
-
 bool force_dma_unencrypted(struct device *dev)
 {
-	return sev_active();
+	return is_prot_virt_guest();
 }
 
 /* protected virtualization */