LF-789-1 Revert "scripts: Makefile: Enable creation of _symbols_ DT node for overlays"

This reverts commit 432071b7a1.

commit: 432071b7a1 scripts: Makefile: Enable creation of _symbols_ DT node for overlays
changes the common Makefile and force creation of __symbols__ node on all platforms.

This is not good and not acceptible under some cases due to this change will increase
the final DTB size a lot and bring big impact for others who does not need creation
of _symbols_ DT node for overlays.For example, on i.MX OP-TEE, the maxsize of DT is 1MB,
this patch will break some of the i.MX6/i.MX7 boards to boot with OP-TEE enabled.

BTW, community has the similar patch but rejected. The following post discuss about this:
https://lore.kernel.org/patchwork/patch/821645/

For specifc plaform/board which need the creation of _symbols_ DT node for overlays, user can
define DTC_FLAGS_target either trough dtc build command line(#1) or with board specific Makefile(#2)

For example:#1

make DTC_FLAGS_fsl-ls1028a-qds=-@ freescale/fsl-ls1028a-qds.dtb

For example:#2

--- a/arch/arm64/boot/dts/freescale/Makefile
+++ b/arch/arm64/boot/dts/freescale/Makefile
@@ -1,4 +1,7 @@
 # SPDX-License-Identifier: GPL-2.0
+# required for overlay support
+#DTC_FLAGS_fsl-ls1028a-qds := -@
+

Signed-off-by: Jason Liu <jason.hui.liu@nxp.com>
Signed-off-by: Dong Aisheng <aisheng.dong@nxp.com>
Reviewed-by: Alex Marginean <alexandru.marginean@nxp.com>
Tested-by: Alex Marginean <alexandru.marginean@nxp.com>
(cherry picked from commit 8d0eaf37fa)

scripts/Makefile.lib

@@ -269,9 +269,6 @@ endif
 
 DTC_FLAGS += $(DTC_FLAGS_$(basetarget))
 
-# Enable creation of _symbols_ node for DT overlays
-DTC_FLAGS += -@
-
 # Generate an assembly file to wrap the output of the device tree compiler
 quiet_cmd_dt_S_dtb= DTB     $@
 cmd_dt_S_dtb=						\