pseries: Fix 64 bit logical memory block panic

Booting with a 4GB LMB size causes us to panic:

  qemu-system-ppc64: OS terminated: OS panic:
      Memory block size not suitable: 0x0

Fix pseries_memory_block_size() to handle 64 bit LMBs.

Cc: stable@vger.kernel.org
Signed-off-by: Anton Blanchard <anton@ozlabs.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200715000820.1255764-1-anton@ozlabs.org

arch/powerpc/platforms/pseries/hotplug-memory.c

@@ -25,7 +25,7 @@
 unsigned long pseries_memory_block_size(void)
 {
 	struct device_node *np;
-	unsigned int memblock_size = MIN_MEMORY_BLOCK_SIZE;
+	u64 memblock_size = MIN_MEMORY_BLOCK_SIZE;
 	struct resource r;
 
 	np = of_find_node_by_path("/ibm,dynamic-reconfiguration-memory");