boards: reel_board: enable pull-up on UART TX pin
boards: reel_board: enable pull-up on UART TX pin

Enable pull-up on UART TX pin to reduce power consumption.
If the board is powered by battery the SoC consumes more
power than expected.
The consumption increases because TX pin is floating
(High-Impedance state of pin B from Dual-Supply Bus Transceiver).

Similar to commit b5b728495b04
("boards: reel_board: enable pull-up on UART RX pin")

Signed-off-by: Johann Fischer <b39b26e1812eb092eb217277792f3735321fa456@phytec.de>

Vudentz/zephyr,Vudentz/zephyr,nashif/zephyr,Vudentz/zephyr,finikorg/zephyr,finikorg/zephyr,finikorg/zephyr,nashif/zephyr,Vudentz/zephyr,finikorg/zephyr,finikorg/zephyr,GiulianoFranchetto/zephyr,zephyrproject-rtos/zephyr,GiulianoFranchetto/zephyr,zephyrproject-rtos/zephyr,GiulianoFranchetto/zephyr,GiulianoFranchetto/zephyr,galak/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,nashif/zephyr,galak/zephyr,galak/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,GiulianoFranchetto/zephyr,nashif/zephyr,Vudentz/zephyr,nashif/zephyr,Vudentz/zephyr,zephyrproject-rtos/zephyr