st/mesa: call nir_lower_flrp only once per shader

Reviewed-by: Connor Abbott <cwabbott0@gmail.com>

src/compiler/shader_info.h

@@ -162,6 +162,9 @@ typedef struct shader_info {
    /** Was this shader linked with any transform feedback varyings? */
    bool has_transform_feedback_varyings;
 
+   /* Whether flrp has been lowered. */
+   bool flrp_lowered;
+
    /* SPV_KHR_float_controls: execution mode for floating point ops */
    unsigned float_controls_execution_mode;