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/zynq_picozed_defconfig b/configs/zynq_picozed_defconfig
index 453cd54..6457876 100644
--- a/configs/zynq_picozed_defconfig
+++ b/configs/zynq_picozed_defconfig
@@ -7,6 +7,7 @@
 CONFIG_DISTRO_DEFAULTS=y
 CONFIG_SYS_CUSTOM_LDSCRIPT=y
 CONFIG_SYS_LDSCRIPT="arch/arm/mach-zynq/u-boot.lds"
+CONFIG_USE_PREBOOT=y
 CONFIG_SPL_STACK_R=y
 CONFIG_SPL_OS_BOOT=y
 CONFIG_SYS_PROMPT="Zynq> "