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/crs305-1g-4s_defconfig b/configs/crs305-1g-4s_defconfig
index df77cb8..c5e2d89 100644
--- a/configs/crs305-1g-4s_defconfig
+++ b/configs/crs305-1g-4s_defconfig
@@ -4,10 +4,11 @@
 CONFIG_SYS_MALLOC_F_LEN=0x2000
 CONFIG_TARGET_CRS305_1G_4S=y
 CONFIG_BUILD_TARGET="u-boot.kwb"
+CONFIG_USE_PREBOOT=y
 CONFIG_SYS_CONSOLE_INFO_QUIET=y
+CONFIG_CMD_BOOTZ=y
 CONFIG_CMD_MEMTEST=y
 CONFIG_SYS_ALT_MEMTEST=y
-CONFIG_CMD_BOOTZ=y
 # CONFIG_CMD_FLASH is not set
 CONFIG_CMD_I2C=y
 CONFIG_CMD_SF=y