intel/vec4: Set the rounding mode

The rounding mode only needs to be set once, because 16-bit floats or
preserving denorms aren't supported for the platforms where vec4 is
used.

Reviewed-by: Emma Anholt <emma@anholt.net>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/20232>

src/intel/compiler/brw_vec4.h

@@ -275,6 +275,8 @@ public:
 
    void resolve_ud_negate(src_reg *reg);
 
+   void emit_shader_float_controls_execution_mode();
+
    bool lower_minmax();
 
    src_reg get_timestamp();