of: clean up OF_CONTROL ifdef conditionals

We have flipped CONFIG_SPL_DISABLE_OF_CONTROL.  We have cleansing
devices, $(SPL_) and CONFIG_IS_ENABLED(), so we are ready to clear
away the ugly logic in include/fdtdec.h:

 #ifdef CONFIG_OF_CONTROL
 # if defined(CONFIG_SPL_BUILD) && !defined(SPL_OF_CONTROL)
 #  define OF_CONTROL 0
 # else
 #  define OF_CONTROL 1
 # endif
 #else
 # define OF_CONTROL 0
 #endif

Now CONFIG_IS_ENABLED(OF_CONTROL) is the substitute.  It refers to
CONFIG_OF_CONTROL for U-boot proper and CONFIG_SPL_OF_CONTROL for
SPL.

Also, we no longer have to cancel CONFIG_OF_CONTROL in
include/config_uncmd_spl.h and scripts/Makefile.spl.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
diff --git a/drivers/serial/serial_omap.c b/drivers/serial/serial_omap.c
index 325fe42..e8d544f 100644
--- a/drivers/serial/serial_omap.c
+++ b/drivers/serial/serial_omap.c
@@ -12,7 +12,7 @@
 
 DECLARE_GLOBAL_DATA_PTR;
 
-#ifdef CONFIG_OF_CONTROL
+#if CONFIG_IS_ENABLED(OF_CONTROL)
 static const struct udevice_id omap_serial_ids[] = {
 	{ .compatible = "ti,omap3-uart" },
 	{ .compatible = "ti,omap4-uart" },