sparc64: Do not set max_mapnr.

There is no need, since nothing relevant to sparc64 makes
use of this value.

Noticed by Sam Ravnborg.
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

arch/sparc/mm/init_64.c

@@ -1751,9 +1751,6 @@ void __init paging_init(void)
 	/* Setup bootmem... */
 	last_valid_pfn = end_pfn = bootmem_init(phys_base);
 
-#ifndef CONFIG_NEED_MULTIPLE_NODES
-	max_mapnr = last_valid_pfn;
-#endif
 	/* Once the OF device tree and MDESC have been setup, we know
 	 * the list of possible cpus.  Therefore we can allocate the
 	 * IRQ stacks.