cursor: Fix "jumping opposite edges" issue when resizing

cursor: Fix "jumping opposite edges" issue when resizing

Commit 08c537e ("xwayland: Honor size increments from
WM_SIZE_HINTS") adjusted only the window width/height according
to the size hints.  If resizing from the top or left edge of the
window, we also need to adjust the window position to keep the
bottom or right edge from jumping around.