pinctrl: sprd: Simplify bool comparison

Fix the following coccicheck warning:
./drivers/pinctrl/sprd/pinctrl-sprd.c:690:8-23: WARNING: Comparison to
bool

Reported-by: Abaci Robot <[e-mail]>
Signed-off-by: YANG LI <[e-mail]>
Reviewed-by: Baolin Wang <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Linus Walleij <[e-mail]>

drivers/pinctrl/sprd/pinctrl-sprd.c

···
 				shift = INPUT_SCHMITT_SHIFT;
 				break;
 			case PIN_CONFIG_BIAS_PULL_UP:
-				if (is_sleep_config == true) {
+				if (is_sleep_config) {
 					val |= SLEEP_PULL_UP;
 					mask = SLEEP_PULL_UP_MASK;
 					shift = SLEEP_PULL_UP_SHIFT;