view.h: changed the type of tiled in struct view to enum view_edge

view.h: changed the type of tiled in struct view to enum view_edge

The type enum view_edge used to be defined in a .c file, so a
structure member 'tiled' in struct view had to be defined to
use another type.

Later (2023-08-02, commit 1ee8715) the definition of enum view_edge
was moved to view.h, so now 'tiled' can be defined to use that type.