st/va: use provided sizes and coords for vlVaGetImage

vlVaGetImage should respect the width, height, and coordinates x and y that
passed in. Therefore, pipe_box should be created with the passed in values
instead of surface width/height.

v2: add input size check, return error when size out of bounds
v3: fix the size check for vaimage
v4: add size adjustment for x and y coordinates

Signed-off-by: Boyuan Zhang <boyuan.zhang@amd.com>
Cc: "18.2" <mesa-stable@lists.freedesktop.org>
Reviewed-by: Leo Liu <leo.liu@amd.com>
Reviewed-by: Ilia Mirkin <imirkin@alum.mit.edu>
Acked-by: Christian König <christian.koenig@amd.com>
(cherry picked from commit d76c2774)