i965/miptree: Fix can_blit_slice()

Check the destination's row pitch against the BLT engine's row pitch
limitation as well.

Fixes: 0288fe8d
("i965/miptree: Use the correct BLT pitch")

v2: Fix the Fixes tag (Dylan).
    Check the destination row pitch (Chris).

Reported-by: Dylan Baker <dylan@pnwbakers.com>
Cc: <mesa-stable@lists.freedesktop.org>
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
(cherry picked from commit b041fc06)