microblaze: Enable MICREL_KSZ9021

To solve enabling ETH_DM where ksz90x1_reg_field is defined only when
additional Micrel type is defined.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>

include/configs/microblaze-generic.h

@@ -342,6 +342,7 @@
 # define CONFIG_PHY_LXT		1
 # define CONFIG_PHY_MARVELL	1
 # define CONFIG_PHY_MICREL	1
+# define CONFIG_PHY_MICREL_KSZ9021
 # define CONFIG_PHY_NATSEMI	1
 # define CONFIG_PHY_REALTEK	1
 # define CONFIG_PHY_VITESSE	1