powerpc/mm: Fix fallthrough bug in hpte_decode

We should not fallthrough different case statements in hpte_decode. Add
break statement to break out of the switch. The regression is introduced by
dcda287a9b26309ae43a091d0ecde16f8f61b4c0 "powerpc/mm: Simplify hpte_decode"

Reported-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/mm/hash_native_64.c

@@ -554,6 +554,7 @@ static void hpte_decode(struct hash_pte *hpte, unsigned long slot,
 			seg_off |= vpi << shift;
 		}
 		*vpn = vsid << (SID_SHIFT - VPN_SHIFT) | seg_off >> VPN_SHIFT;
+		break;
 	case MMU_SEGSIZE_1T:
 		/* We only have 40 - 23 bits of seg_off in avpn */
 		seg_off = (avpn & 0x1ffff) << 23;
@@ -563,6 +564,7 @@ static void hpte_decode(struct hash_pte *hpte, unsigned long slot,
 			seg_off |= vpi << shift;
 		}
 		*vpn = vsid << (SID_SHIFT_1T - VPN_SHIFT) | seg_off >> VPN_SHIFT;
+		break;
 	default:
 		*vpn = size = 0;
 	}