There are two cases which we may use a wrong texture size.
1. A pixmap is modified by the client side after it created
it. Then the pixmap's width may mismatch the original fbo/tex's
size. Thus we need to check this condition when preparing
upload the pixmap.
2. We provide two API to download/upload sub region of a
textured pixmap. The caller may pass in a larger width then
the original pixmap's size, this may happen at putimage
and setspans. We need to validate the width and height
when do the downloading/uploading.
Signed-off-by: Zhigang Gong <zhigang.gong@linux.intel.com>