Convert CONFIG_USE_PREBOOT and CONFIG_PREBOOT to Kconfig

This converts the following to Kconfig:
   CONFIG_USE_PREBOOT
   CONFIG_PREBOOT

Both are together in one commit, since otherwise the former causes kconfig
to define the latter, which gives duplicate symbol errors.

Includes a manual fixup for CONFIG_PREBOOT in ids8313_defconfig since the
backslash lands in the wrong place. Similarly with socfpga_vining_fpga.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/configs/meesc_dataflash_defconfig b/configs/meesc_dataflash_defconfig
index 0bef67e..4794662 100644
--- a/configs/meesc_dataflash_defconfig
+++ b/configs/meesc_dataflash_defconfig
@@ -6,9 +6,11 @@
 CONFIG_ENV_SIZE=0x4200
 CONFIG_ENV_OFFSET=0x4200
 CONFIG_NR_DRAM_BANKS=1
+CONFIG_ENV_SECT_SIZE=0x210
 CONFIG_FIT=y
 CONFIG_SYS_EXTRA_OPTIONS="AT91SAM9263,SYS_USE_DATAFLASH"
 CONFIG_BOOTDELAY=3
+CONFIG_USE_PREBOOT=y
 CONFIG_MISC_INIT_R=y
 CONFIG_BOARD_EARLY_INIT_F=y
 CONFIG_HUSH_PARSER=y
@@ -24,7 +26,6 @@
 CONFIG_ENV_IS_IN_SPI_FLASH=y
 CONFIG_USE_ENV_SPI_MAX_HZ=y
 CONFIG_ENV_SPI_MAX_HZ=15000000
-CONFIG_ENV_SECT_SIZE=0x210
 CONFIG_DM=y
 CONFIG_CLK=y
 CONFIG_CLK_AT91=y