fdt: Make OF_BOARD a bool option

This should not be a separate option from OF_SEPARATE. It is a run-time
option to override the devicetree, even if present.

Move the option out of the choice.

Disable BINMAN_FDT for a few boards which don't actually use it.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/configs/qemu-riscv32_spl_defconfig b/configs/qemu-riscv32_spl_defconfig
index c442296..8889b02 100644
--- a/configs/qemu-riscv32_spl_defconfig
+++ b/configs/qemu-riscv32_spl_defconfig
@@ -6,6 +6,7 @@
 CONFIG_SPL=y
 CONFIG_TARGET_QEMU_VIRT=y
 CONFIG_RISCV_SMODE=y
+# CONFIG_OF_BOARD_FIXUP is not set
 CONFIG_DISTRO_DEFAULTS=y
 CONFIG_SYS_LOAD_ADDR=0x80200000
 CONFIG_FIT=y
@@ -18,3 +19,4 @@
 CONFIG_SYS_RELOC_GD_ENV_ADDR=y
 CONFIG_DM_MTD=y
 CONFIG_SYSRESET_SBI=y
+# CONFIG_BINMAN_FDT is not set