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/portl2_defconfig b/configs/portl2_defconfig
index a745574..1c6dad9 100644
--- a/configs/portl2_defconfig
+++ b/configs/portl2_defconfig
@@ -26,6 +26,7 @@
 CONFIG_CMD_UBI=y
 # CONFIG_CMD_UBIFS is not set
 CONFIG_ENV_IS_IN_EEPROM=y
+CONFIG_BOOTCOUNT_LIMIT=y
 # CONFIG_MMC is not set
 CONFIG_SPI_FLASH=y
 CONFIG_SPI_FLASH_STMICRO=y