drivers/serial: stm32: Modify Kconfig instance flags

STM32 uart Kconfig instance flags were not following
same naming scheme than other drivers (i2c, spi, ..)

Update driver to use UART_X instead of UART_STM32_PORT_X

Signed-off-by: Erwan Gouriou <erwan.gouriou@linaro.org>
97 files changed