pinctrl: fix loop in k210_pinconf_get_drive()

The loop exited too early so the k210_pinconf_drive_strength[0] array
element was never used.

Fixes: d4c34d09 ("pinctrl: Add RISC-V Canaan Kendryte K210 FPIOA driver")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>
Reviewed-by: Sean Anderson <seanga2@gmail.com>
Link: https://lore.kernel.org/r/20220209180804.GA18385@kiliSigned-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/pinctrl/pinctrl-k210.c

@@ -482,7 +482,7 @@ static int k210_pinconf_get_drive(unsigned int max_strength_ua)
 {
 	int i;
 
-	for (i = K210_PC_DRIVE_MAX; i; i--) {
+	for (i = K210_PC_DRIVE_MAX; i >= 0; i--) {
 		if (k210_pinconf_drive_strength[i] <= max_strength_ua)
 			return i;
 	}