mesa: Fix incorrect access parameter passed to MapBuffer

mesa: Fix incorrect access parameter passed to MapBuffer

The code previously passed GL_DYNAMIC_DRAW for the access parameter.
By inspection, I believe that all drivers would treat this as
GL_READ_WRITE because it's not GL_READ_ONLY and it's not
GL_WRITE_ONLY.

It appears the i965 code wants GL_WRITE_ONLY (it's about to write a
bunch of data in, never read data), while the arrayelt code is
GL_READ_ONLY (just dereffed as arguments to CALL_Whatever*v).

Signed-off-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Brian Paul <brianp@vmware.com>
Acked-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Eric Anholt <eric@anholt.net>
Reviewed-by: Keith Whitwell <keithw@vmware.com>