boards: arm: lpcxpresso55s36: document the CAN IOs used

List the IOs used for the CAN RXD/TXD lines in the board documentation.

Signed-off-by: Henrik Brix Andersen <hebad@vestas.com>

boards/arm/lpcxpresso55s36/doc/index.rst

diff --git a/boards/arm/lpcxpresso55s36/doc/index.rst b/boards/arm/lpcxpresso55s36/doc/index.rst
index 01bade6..8e9e358 100644
--- a/boards/arm/lpcxpresso55s36/doc/index.rst
+++ b/boards/arm/lpcxpresso55s36/doc/index.rst
@@ -133,7 +133,10 @@
 +---------+-----------------+----------------------------+
 | PIO0_31 | FLEXPPWM1_PWM2_B| pwm                        |
 +---------+-----------------+----------------------------+
-
+| PIO1_2  | CAN0_TXD        | CAN TX                     |
++---------+-----------------+----------------------------+
+| PIO1_3  | CAN0_RXD        | CAN RX                     |
++---------+-----------------+----------------------------+
 
 System Clock
 ============