mm/memblock: drop WARN and use SMP_CACHE_BYTES as a default alignment

Don't produce warning and interpret 0 as "default align" equal to
SMP_CACHE_BYTES in case if caller of memblock_alloc_base_nid() doesn't
specify alignment for the block (align == 0).

This is done in preparation of introducing common memblock alloc interface
to make code behavior consistent.  More details are in below thread :

	https://lkml.org/lkml/2013/10/13/117.
Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.com>
Signed-off-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Cc: Yinghai Lu <yinghai@kernel.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Christoph Lameter <cl@linux-foundation.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Paul Walmsley <paul@pwsan.com>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Tony Lindgren <tony@atomide.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/memblock.c

@@ -969,8 +969,8 @@ static phys_addr_t __init memblock_alloc_base_nid(phys_addr_t size,
 {
 	phys_addr_t found;
 
-	if (WARN_ON(!align))
-		align = __alignof__(long long);
+	if (!align)
+		align = SMP_CACHE_BYTES;
 
 	/* align @size to avoid excessive fragmentation on reserved array */
 	size = round_up(size, align);