sparc64: Register hugepages during arch init

Add hstate for each supported hugepage size using
arch initcall. This change fixes some hugepage
parameter parsing inconsistencies:

case 1: no hugepage parameters

 Without hugepage parameters, only a hugepages-8192kB entry is visible
 in sysfs.  It's different from x86_64 where both 2M and 1G hugepage
 sizes are available.

case 2: default_hugepagesz=[64K|256M|2G]

 When specifying only a default_hugepagesz parameter, the default
 hugepage size isn't really changed and it stays at 8M. This is again
 different from x86_64.

Orabug: 25869946

Reviewed-by: Bob Picco <bob.picco@oracle.com>
Signed-off-by: Nitin Gupta <nitin.m.gupta@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>