sparc/mm/hugepages: Fix setup_hugepagesz for invalid values.

hugetlb_bad_size needs to be called on invalid values.  Also change the
pr_warn to a pr_err to better align with other platforms.

Signed-off-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>