drivers: uart_stm32: fix device is ready for tx dma in async init
drivers: uart_stm32: fix device is ready for tx dma in async init

Fixes TX DMA device is ready check in async initialization function.

Signed-off-by: Georgij Cernysiov <bd22e7942bc8beaebb3a0cc77ee92e4585e26366@gmail.com>

galak/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,finikorg/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,galak/zephyr,finikorg/zephyr