Convert CONFIG_BOOTFILE to Kconfig

This converts the following to Kconfig:
   CONFIG_BOOTFILE

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/stih410-b2260_defconfig b/configs/stih410-b2260_defconfig
index 90a4ec4..e99bb1e 100644
--- a/configs/stih410-b2260_defconfig
+++ b/configs/stih410-b2260_defconfig
@@ -25,6 +25,8 @@
 # CONFIG_ISO_PARTITION is not set
 CONFIG_OF_CONTROL=y
 CONFIG_SYS_RELOC_GD_ENV_ADDR=y
+CONFIG_USE_BOOTFILE=y
+CONFIG_BOOTFILE="uImage"
 CONFIG_REGMAP=y
 CONFIG_SYSCON=y
 CONFIG_CLK=y