Fix PV datalign when for values starting prior to MDA area.

Fix PV datalign when for values starting prior to MDA area.

The dataalign value must always be aligned according
to MDA area.
The currect code checks if calculated value collides with
MDA area but not if the value is so small that it is
located before MDA starts.

Unfortunatelly there can be also MDA in the end of the device.

The patch adds simple check to avoid this miscalculation.
Patch expects that first MDA always starts on <= pagesize boundary
(this is true for all allowed label sector parameters).