glsl: initialize data.precision value in ir_variable constructor

Signed-off-by: Samuel Iglesias Gonsálvez <siglesias@igalia.com>
Reviewed-by: Tapani Pälli <tapani.palli@intel.com>

src/glsl/ir.cpp

@@ -1676,6 +1676,7 @@ ir_variable::ir_variable(const struct glsl_type *type, const char *name,
    this->data.interpolation = INTERP_QUALIFIER_NONE;
    this->data.max_array_access = 0;
    this->data.atomic.offset = 0;
+   this->data.precision = GLSL_PRECISION_NONE;
    this->data.image_read_only = false;
    this->data.image_write_only = false;
    this->data.image_coherent = false;