i965: Move _mesa_ir_link_shader call before device-specific linking

i965: Move _mesa_ir_link_shader call before device-specific linking

_mesa_ir_link_shader needs to be called before cloning the IR tree so
that the var->location field for uniforms is set.

WARNING: This change breaks several integer division related piglit
tests.  The tests break because _mesa_ir_link_shader lowers integer
division to an RCP followed by a MUL.  The fix is to factor out more
of the code from ir_to_mesa so that _mesa_ir_link_shader does not need
to be called at all by the i965 driver.  This will be the subject of
several follow-on patches.

Signed-off-by: Ian Romanick <ian.d.romanick@intel.com>
Tested-by: Tom Stellard <thomas.stellard@amd.com>