KM: add CONFIG_KM_COMMON_ETH_INIT for km common eth init

This must be defined by a board support file that want to use the
keymile common.c board_eth_init function that requires ethernet_present
to be defined.

Currently all the km architectures use it but the kmp204x architecture
later supported in this series does use another board_eth_init function
and thus does not define it.

Signed-off-by: Valentin Longchamp <valentin.longchamp@keymile.com>
diff --git a/include/configs/km/km-powerpc.h b/include/configs/km/km-powerpc.h
index 15fef24..2cebb2b 100644
--- a/include/configs/km/km-powerpc.h
+++ b/include/configs/km/km-powerpc.h
@@ -17,6 +17,9 @@
 #define CONFIG_CMD_DTT
 #define CONFIG_JFFS2_CMDLINE
 
+/* standard km ethernet_present for piggy */
+#define CONFIG_KM_COMMON_ETH_INIT
+
 /* EEprom support 24C08, 24C16, 24C64 */
 #define CONFIG_SYS_I2C_MULTI_EEPROMS
 #define CONFIG_SYS_EEPROM_PAGE_WRITE_ENABLE