glsl/ast: Use ir_binop_equal instead of ir_binop_all_equal

glsl/ast: Use ir_binop_equal instead of ir_binop_all_equal

The values being compared are scalars, so these are the same.  While
I'm here, simplify the run_default condition to just deref the flag
(instead of comparing a scalar bool with true).

There is a bit of extra change in this patch.  When constructing an
ir_binop_equal ir_expression, there is an assertion that the types are
the same.  There is no such assertion for ir_binop_all_equal, so
passing glsl_type::uint_type with glsl_type::int_type was previously
fine.  A bunch of the code motion is to deal with that.

Signed-off-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Alejandro Piñeiro <apinheiro@igalia.com>