drivers: display: stm32_ltdc: fix set orientation API
drivers: display: stm32_ltdc: fix set orientation API

Refactors invalid switch into if statement.
Fixes orientation set return value for normal
display orientation.

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

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