Windows: fix eina_file_map_new()

Windows: fix eina_file_map_new()

the offset passed to MapViewOfFile() must be a multiple of the granularity.

https://docs.microsoft.com/en-us/windows/win32/memory/creating-a-view-within-a-file is taken as basis for this patch

Reviewed-by: Stefan Schmidt <stefan@datenfreihafen.org>
Reviewed-by: Wander Lairson Costa <wander.lairson@gmail.com>
Differential Revision: https://phab.enlightenment.org/D12031