mpc85xx: add socrates dts from linux

add socrates device tree from linux:

commit 71ae5fc87c34 ("Merge tag 'linux-kselftest-5.2-rc1' of
git://git.kernel.org/pub/scm/linux/kernel/git/shuah/linux-kselftest")

and added SPDX license identifier.
Did not fix checkpatch warnings:
arch/powerpc/dts/socrates.dts:235: check: Please don't use multiple blank lines
arch/powerpc/dts/socrates.dts:238: error: code indent should use tabs where possible

Also, add me as board maintainer.

Signed-off-by: Heiko Schocher <hs@denx.de>
Reviewed-by: Priyanka Jain <priyanka.jain@nxp.com>
diff --git a/arch/powerpc/dts/Makefile b/arch/powerpc/dts/Makefile
index 021c85f..3195351 100644
--- a/arch/powerpc/dts/Makefile
+++ b/arch/powerpc/dts/Makefile
@@ -8,6 +8,7 @@
 dtb-$(CONFIG_TARGET_P3041DS) += p3041ds.dtb
 dtb-$(CONFIG_TARGET_P4080DS) += p4080ds.dtb
 dtb-$(CONFIG_TARGET_P5040DS) += p5040ds.dtb
+dtb-$(CONFIG_TARGET_SOCRATES) += socrates.dtb
 dtb-$(CONFIG_TARGET_T1024RDB) += t1024rdb.dtb
 dtb-$(CONFIG_TARGET_T1042D4RDB) += t1042d4rdb.dtb
 dtb-$(CONFIG_TARGET_T2080QDS) += t2080qds.dtb