intel: Skip texsubimage fastpath for more pixel unpack state (v2)

intel: Skip texsubimage fastpath for more pixel unpack state (v2)

Fixes piglit tests "unpack-teximage2d --pbo=* --format=GL_BGRA" on
Sandybridge+.

The fastpath was checking an incomplete set of pixel unpack state. This
patch adds checks for all the fields of gl_pixelstore_attrib that affect
2D texture uploads.  Also, it begins permitting the case where
GL_UNPACK_ROW_LENGTH is 0.

Ideally, we would just ask a unicorn to JIT this fastpath for us in
a way that safely handles the unpacking state. Until then, it's safer if
only a small set of situations activate the fastpath.

v2: Use _mesa_is_bufferobj(), per Anholt.

Reviewed-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Chad Versace <chad.versace@linux.intel.com>