ARM: dts: sync armv7-m.dtsi with kernel v5.10-rc1

ARM: dts: sync armv7-m.dtsi with kernel v5.10-rc1

Since kernel v4.8-rc1, commit 05b23ebc2bd9 ("ARM: dts: armv7-m: remove skeleton.dtsi include"),
skeleton.dtsi file is no more included.

This synchronization is needed to avoid to get 2 memory node
in DTB file if, in DTS file, memory node is declared with the correct
syntax as following:

	memory@90000000 {
 		device_type = "memory";
 		reg = <0x90000000 0x800000>;
 	};

Then in DTB, we will have the 2 memory nodes, which is incorrect and
cause misbehavior during DT parsing by U-boot:

	memory {
		device_type = "memory";
		reg = <0x00 0x00>;
	};

	memory@90000000 {
		device_type = "memory";
		reg = <0x90000000 0x800000>;
	};

Issue found when synchronizing MCU's STM32 DT from kernel v5.10-rc1.
When using fdtdec_setup_mem_size_base() or fdtdec_setup_memory_banksize()
API, first above memory node is found (with reg = <0x00 0x00>), so
gd->ram_size, gd->ram_base, gd->bd->bi_dram[bank].start and
gd->bd->bi_dram[bank].size are all set to 0 which avoid boards to boot.

Signed-off-by: Patrice Chotard <patrice.chotard@st.com>
Reviewed-by: Patrick Delaunay <patrick.delaunay@st.com>