mb/siemens/mc_ehl2: Enable TSN GbE driver

This variant uses all three EHL Ethernet GbE-TSN Controller so enable
the TSN GbE driver in order to set the needed MAC addresses. The
required function to retrieve a valid MAC address was already implement
in the common mainboard.c for mc_ehl.

TEST:
- Boot mc_ehl2 into Linux and check MAC addr via 'ip a'

Change-Id: Ia052c44feb606f9e1d31d047f2acc67e3226a895
Signed-off-by: Mario Scheithauer <mario.scheithauer@siemens.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/63864
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Werner Zeh <werner.zeh@siemens.com>

src/mainboard/siemens/mc_ehl/variants/mc_ehl2/Kconfig

@@ -4,6 +4,7 @@ config BOARD_SPECIFIC_OPTIONS
 	def_bool y
 	select DRIVER_INTEL_I210
 	select SOC_INTEL_COMMON_BLOCK_LPC_COMB_ENABLE
+	select EHL_TSN_DRIVER
 
 config FMDFILE
 	default "src/mainboard/\$(CONFIG_MAINBOARD_DIR)/mc_ehl.fmd"