Improvement to am335x_lcd_calc_divisor()

[Leonardo Fogel]

I just realized the last proposal would depend on 64-bit multiplication, which may not be available. Here is another approach:

Let f be the fractional part of r, the real number (R%F)/F. If f >= 0.5, then lround(r) rounds up. We can test the multiplicative inverse of f, 1/f, F/(R%F). If 1/f <= 2, then lround(r) rounds up.

	if (freq == 0) /* there is a bug somewhere. */
		return (255);

	if ((reference%freq > 0) && (freq/(reference%freq) <= 2))
		div = reference/freq + 1; /* rounds up   */
	else
		div = reference/freq;     /* rounds down */

	/* Raster mode case: divisors are in range from 2 to 255 */
	if (div < 2)
		div = 2;
	else if (div > 255)
		dir = 255;

	return (div);

Thank you.
Leonardo