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/brppt1_mmc_defconfig b/configs/brppt1_mmc_defconfig
index 5487e55..94b9bab 100644
--- a/configs/brppt1_mmc_defconfig
+++ b/configs/brppt1_mmc_defconfig
@@ -19,6 +19,8 @@
 CONFIG_BOOTDELAY=0
 CONFIG_USE_BOOTCOMMAND=y
 CONFIG_BOOTCOMMAND="run b_default"
+CONFIG_USE_PREBOOT=y
+CONFIG_PREBOOT="run cfgscr; run brdefaultip"
 CONFIG_SYS_CONSOLE_IS_IN_ENV=y
 CONFIG_SYS_CONSOLE_OVERWRITE_ROUTINE=y
 CONFIG_SYS_CONSOLE_INFO_QUIET=y