cpu: use ROUND_UP() to define xxx_PAGE_ALIGN

cpu: use ROUND_UP() to define xxx_PAGE_ALIGN

Use ROUND_UP() to define, which is a little bit easy to read.

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Wei Yang <richardw.yang@linux.intel.com>
Message-Id: <20191013021145.16011-2-richardw.yang@linux.intel.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>