i2c: riic: Allow setting frequencies lower than 50KHz

The MR1.CKS field is 3 bits wide and all the possible values (from 0 to
7) are valid. This is true for all the SoCs currently integrated in
upstream Linux. Take into account CKS=7 which allows setting bus
frequencies lower than 50KHz. This may be useful at least for debugging.

Fixes: d982d6651419 ("i2c: riic: remove clock and frequency restrictions")
Signed-off-by: Claudiu Beznea <[e-mail]>
Signed-off-by: Wolfram Sang <[e-mail]>

drivers/i2c/busses/i2c-riic.c

···
 	 */
 	total_ticks = DIV_ROUND_UP(rate, t->bus_freq_hz ?: 1);
 
-	for (cks = 0; cks < 7; cks++) {
+	for (cks = 0; cks <= 7; cks++) {
 		/*
 		 * 60% low time must be less than BRL + 2 + 1
 		 * BRL max register value is 0x1F.