nir/glsl: Remove dead function parameter handling code

nir/glsl: Remove dead function parameter handling code

NIR has never been used on IR where we haven't already done function
inlining so this code has been dead from the beginning.  Let's just get rid
of it for now.  We can always put it back in if we decide to use NIR for
function inlining at some point in the future.

Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>