i965: Clean up brwNewProgram().

i965: Clean up brwNewProgram().

All shader stages do the exact same thing, so we don't need the switch
statement, or the redundant FS case.  I believe these used to be
different before Tim eliminated the (e.g.) brw_vertex_program
subclasses.

Reviewed-by: Tapani Pälli <tapani.palli@intel.com>
Reviewed-by: Timothy Arceri <tarceri@itsqueeze.com>