glsl: Pick ast_conditional branch regardless of op1/2 being constant.

glsl: Pick ast_conditional branch regardless of op1/2 being constant.

If the ?: operator's condition is a constant value, and both branches
were pure expressions, we can just make the resulting value one or the
other.

Previously, we only did this if op[1] and op[2] were also constant
values - but there's no actual reason for that restriction.

No changes in shader-db, probably because we usually optimize this later
anyway.  But it does make us generate less stupid code up front.

Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Matt Turner <mattst88@gmail.com>