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_defconfig b/configs/CHIP_defconfig
index 95c564c..7868108 100644
--- a/configs/CHIP_defconfig
+++ b/configs/CHIP_defconfig
@@ -6,6 +6,7 @@
 CONFIG_DRAM_TIMINGS_DDR3_800E_1066G_1333J=y
 CONFIG_USB0_VBUS_PIN="PB10"
 CONFIG_VIDEO_COMPOSITE=y
+CONFIG_USE_PREBOOT=y
 CONFIG_SPL_I2C_SUPPORT=y
 CONFIG_CMD_DFU=y
 CONFIG_CMD_USB_MASS_STORAGE=y