mfd: stmpe: PWM on 24xx has altfunc 1

On the STMPE2401 and STMPE2401 altfunction 1 corresponds to the
PWM channels. This oneliner was missing in the case-switch, making
it impossible to enable the PWM channel output.
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>

drivers/mfd/stmpe.c

@@ -795,6 +795,7 @@ static int stmpe24xx_get_altfunc(struct stmpe *stmpe, enum stmpe_block block)
 		return 2;
 
 	case STMPE_BLOCK_KEYPAD:
+	case STMPE_BLOCK_PWM:
 		return 1;
 
 	case STMPE_BLOCK_GPIO: