boards: update IS_PIN_SERIAL for Teensy 3.5 & 3.6

Signed-off-by: Petros Angelatos <petrosagg@gmail.com>

Author: petrosagg

Boards.h

@@ -414,7 +414,7 @@ writePort(port, value, bitmask):  Write an 8 bit port.
 #define IS_PIN_PWM(p)           digitalPinHasPWM(p)
 #define IS_PIN_SERVO(p)         ((p) >= 0 && (p) < MAX_SERVOS)
 #define IS_PIN_I2C(p)           ((p) == 18 || (p) == 19)
-#define IS_PIN_SERIAL(p)        (((p) > 6 && (p) < 11) || ((p) == 0 || (p) == 1))
+#define IS_PIN_SERIAL(p)        (((p) > 6 && (p) < 11) || ((p) == 0 || (p) == 1) || ((p) > 30 && (p) < 35) || ((p) == 47 || (p) == 48))
 #define PIN_TO_DIGITAL(p)       (p)
 // A0-A9 = D14-D23; A12-A20 = D31-D39; A23-A24 = D49-D50; A10-A11 = D64-D65; A21-A22 = D66-D67; A25-A26 = D68-D69
 #define PIN_TO_ANALOG(p)        (((p) <= 23) ? (p) - 14 : (((p) <= 39) ? (p) - 19 : (((p) <= 50) ? (p) - 26 : (((p) <= 65) ? (p) - 55 : (((p) <= 67) ? (p) - 45 : (p) - 43)))))