mdadm/super1: Add MD_FEATURE_RAID0_LAYOUT if kernel>=5.4

mdadm/super1: Add MD_FEATURE_RAID0_LAYOUT if kernel>=5.4

After and include kernel v5.4, it adds one feature bit MD_FEATURE_RAID0_LAYOUT.
It must need to specify a layout for raid0 with more than one zone. But for
raid0 with one zone, in fact it also has a defalut layout.

Now for raid0 with one zone, *unknown* layout can be seen when running mdadm -D
command. It's the reason that mdadm doesn't set MD_FEATURE_RAID0_LAYOUT for
raid0 with one zone. Then in kernel space, super_1_validate sets mddev->layout
to -1 because of no MD_FEATURE_RAID0_LAYOUT. In fact, in raid0 io path, it
uses the default layout. Set raid0_need_layout to true if kernel_version<=v5.4.

Fixes: 329dfc28debb ('Create: add support for RAID0 layouts.')
Signed-off-by: Xiao Ni <xni@redhat.com>
Reviewed-by: Mariusz Tkaczyk <mariusz.tkaczyk@linux.intel.com>
Signed-off-by: Jes Sorensen <jes@trained-monkey.org>