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/P1010RDB-PA_36BIT_SDCARD_defconfig b/configs/P1010RDB-PA_36BIT_SDCARD_defconfig
index dc113be..a9ecce9 100644
--- a/configs/P1010RDB-PA_36BIT_SDCARD_defconfig
+++ b/configs/P1010RDB-PA_36BIT_SDCARD_defconfig
@@ -47,6 +47,8 @@
 CONFIG_ENV_OVERWRITE=y
 CONFIG_ENV_IS_IN_MMC=y
 CONFIG_SYS_RELOC_GD_ENV_ADDR=y
+CONFIG_USE_BOOTFILE=y
+CONFIG_BOOTFILE="uImage"
 CONFIG_DM=y
 CONFIG_SYS_SATA_MAX_DEVICE=2
 CONFIG_FSL_CAAM=y