i965: Simplify brw_get_renderer_string()

i965: Simplify brw_get_renderer_string()

This stops using driGetRendererString() in favor of a simple snprintf().
This should have the same functionality on 64-bit systems, but drops
a "x86/MMX/SSE2" suffix on 32-bit systems.  (People shouldn't be using
the GL_RENDERER string to check for CPU features...)

We also use gen_get_device_name() instead of PCI ID list munging.

Reviewed-by: Matt Turner <mattst88@gmail.com>
Reviewed-by: Caio Marcelo de Oliveira Filho <caio.oliveira@intel.com>
Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/merge_requests/3371>