samples: remove CONFIG_MBOX_STM32_HSEM enabling in conf files

Now that the MBOX_STM32_HSEM driver is enabled by default if
present within the device-tree, it is no more necessary to
manually enable it within samples board specific conf files.

Remove as well the CONFIG_LOG_BACKEND_UART since overall
CONFIG_LOG is anyway not enabled in the samples/drivers/mbox

Signed-off-by: Alain Volmat <[email protected]>

Author: Alain Volmat

samples/drivers/mbox/boards/stm32h747i_disco_stm32h747xx_m7.conf

@@ -1,5 +1,2 @@
 CONFIG_CONSOLE=y
 CONFIG_UART_CONSOLE=y
-CONFIG_LOG_BACKEND_UART=y
-
-CONFIG_MBOX_STM32_HSEM=y

samples/drivers/mbox/remote/boards/stm32h747i_disco_stm32h747xx_m4.conf

@@ -1,5 +1,3 @@
 CONFIG_CONSOLE=y
 CONFIG_UART_CONSOLE=y
 CONFIG_LOG_BACKEND_UART=y
-
-CONFIG_MBOX_STM32_HSEM=y