Convert CONFIG_FSL_IIM to Kconfig

This converts the following to Kconfig:
   CONFIG_FSL_IIM

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/mx51evk_defconfig b/configs/mx51evk_defconfig
index 89597c0..d76ebe8 100644
--- a/configs/mx51evk_defconfig
+++ b/configs/mx51evk_defconfig
@@ -40,6 +40,7 @@
 CONFIG_USE_ETHPRIME=y
 CONFIG_ETHPRIME="FEC0"
 CONFIG_ARP_TIMEOUT=200
+CONFIG_FSL_IIM=y
 CONFIG_FSL_ESDHC_IMX=y
 CONFIG_MTD=y
 CONFIG_PHYLIB=y