i965: Make brwInitFunctions take brw_context rather than intel_screen.

i965: Make brwInitFunctions take brw_context rather than intel_screen.

It actually just wants generation checking, and brw->gen is the usual
way of doing that.  In the future, we'll also want to check brw->hw_ctx,
which isn't available from the screen.

While we're changing the function signature, convert from camel case to
our usual naming conventions.

Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>