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/CHIP_pro_defconfig b/configs/CHIP_pro_defconfig
index 6cd500f..8299421 100644
--- a/configs/CHIP_pro_defconfig
+++ b/configs/CHIP_pro_defconfig
@@ -5,6 +5,7 @@
 CONFIG_MACH_SUN5I=y
 CONFIG_DRAM_TIMINGS_DDR3_800E_1066G_1333J=y
 CONFIG_USB0_VBUS_PIN="PB10"
+CONFIG_USE_PREBOOT=y
 CONFIG_SPL_I2C_SUPPORT=y
 # CONFIG_CMD_FLASH is not set
 CONFIG_CMD_MTDPARTS=y