Convert CONFIG_BOOTCOUNT_LIMIT to Kconfig

This converts the following to Kconfig:
   CONFIG_BOOTCOUNT_LIMIT

Signed-off-by: Lukasz Majewski <lukma@denx.de>
Tested-by: Alex Kiernan <alex.kiernan@gmail.com>
Reviewed-by: Hannes Schmelzer <hannes.schmelzer@br-automation.com>
Acked-by: Hannes Schmelzer <hannes.schmelzer@br-automation.com>
diff --git a/configs/thuban_defconfig b/configs/thuban_defconfig
index df76145..4a3c0cd 100644
--- a/configs/thuban_defconfig
+++ b/configs/thuban_defconfig
@@ -51,6 +51,7 @@
 CONFIG_OF_CONTROL=y
 CONFIG_OF_EMBED=y
 CONFIG_ENV_IS_IN_NAND=y
+CONFIG_BOOTCOUNT_LIMIT=y
 CONFIG_DFU_NAND=y
 CONFIG_MMC_OMAP_HS=y
 CONFIG_NAND=y