util: Tiny optimisation for the linear→srgb conversion

When converting 0.0 it would be nice if it didn't do any arithmetic.

Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>

src/util/format_srgb.h

@@ -57,7 +57,7 @@ util_format_linear_to_srgb_helper_table[104];
 static inline float
 util_format_linear_to_srgb_float(float cl)
 {
-   if (cl < 0.0f)
+   if (cl <= 0.0f)
       return 0.0f;
    else if (cl < 0.0031308f)
       return 12.92f * cl;