pinctrl: bcm: Simplify bool comparison

Fix the follow coccicheck warnings:

./drivers/pinctrl/bcm/pinctrl-ns2-mux.c:856:29-38: WARNING:
Comparison to bool.

Reported-by: Abaci Robot <[e-mail]>
Signed-off-by: Jiapeng Zhong <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Linus Walleij <[e-mail]>

drivers/pinctrl/bcm/pinctrl-ns2-mux.c

···
 	switch (param) {
 	case PIN_CONFIG_BIAS_DISABLE:
 		ns2_pin_get_pull(pctldev, pin, &pull_up, &pull_down);
-		if ((pull_up == false) && (pull_down == false))
+		if (!pull_up && !pull_down)
 			return 0;
 		else
 			return -EINVAL;