drivers: ssd1306: remove SPI operation flags
drivers: ssd1306: remove SPI operation flags

Remove two operation flags in the SPI configuration
instance, which disturb software controlled chip select
lines (CS never gets released).

Signed-off-by: Marco Peter <3829486b93ec44395f0b980424bae9b6fb07b7bc@peter-net.ch>

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