ARM: configs: at91_dt_defconfig: add useful helper options

Add GPIO, SPI and I2C options that were missing from the
at91_dt_defconfig whereas they were in sama5_defconfig. It unifies all
AT91 defconfigs with same set of useful options.
Signed-off-by: Nicolas Ferre <nicolas.ferre@microchip.com>

arch/arm/configs/at91_dt_defconfig

@@ -107,12 +107,15 @@ CONFIG_LEGACY_PTY_COUNT=4
 CONFIG_SERIAL_ATMEL=y
 CONFIG_SERIAL_ATMEL_CONSOLE=y
 CONFIG_HW_RANDOM=y
+CONFIG_I2C_CHARDEV=y
 CONFIG_I2C_AT91=y
 CONFIG_I2C_GPIO=y
 CONFIG_SPI=y
 CONFIG_SPI_ATMEL=y
 CONFIG_SPI_ATMEL_QUADSPI=y
+CONFIG_SPI_GPIO=y
 CONFIG_PINCTRL_MCP23S08=m
+CONFIG_GPIO_SYSFS=y
 CONFIG_POWER_RESET=y
 CONFIG_POWER_SUPPLY=y
 # CONFIG_HWMON is not set