freedreno/a3xx: only enable blend clamp for non-float formats
This fixes arb_color_buffer_float-render GL_RGBA16F. Signed-off-by:Ilia Mirkin <imirkin@alum.mit.edu> Cc: "10.3 10.4" <mesa-stable@lists.freedesktop.org> Reviewed-by:
Rob Clark <robclark@freedesktop.org>