glsl: add _mesa_glsl_parse_state object to is_lvalue()

glsl: add _mesa_glsl_parse_state object to is_lvalue()

Yes, this is a bit hacky but we don't really have the choice.
Plain GLSL doesn't accept bindless samplers/images as l-values
while it's allowed when ARB_bindless_texture is enabled.

The default NULL parameter is because we can't access the
_mesa_glsl_parse_state object in few places in the compiler.
One is_lvalue(NULL) call is for IR validation but other checks
happen elsewhere, should be safe.

Signed-off-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Reviewed-by: Nicolai Hähnle <nicolai.haehnle@amd.com>
Reviewed-by: Timothy Arceri <tarceri@itsqueeze.com>