This adds the following commits from upstream:

aadd0b65c987 checks: centralize printing of property names in failure messages
88960e398907 checks: centralize printing of node path in check_msg
f1879e1a50eb Add limited read-only support for older (V2 and V3) device tree to libfdt.
37dea76e9700 srcpos: drop special handling of tab
65893da4aee0 libfdt: overlay: Add missing license
962a45ca034d Avoid installing pylibfdt when dependencies are missing
cd6ea1b2bea6 Makefile: Split INSTALL out into INSTALL_{PROGRAM,LIB,DATA,SCRIPT}
51b3a16338df Makefile.tests: Add LIBDL make(1) variable for portability sake
333d533a8f4d Attempt to auto-detect stat(1) being used if not given proper invocation
e54388015af1 dtc: Bump version to v1.4.6
a1fe86f380cb fdtoverlay: Switch from using alloca to malloc
c8d5472de3ff tests: Improve compatibility with other platforms
c81d389a10cc checks: add chosen node checks
e671852042a7 checks: add aliases node checks
d0c44ebe3f42 checks: check for #{size,address}-cells without child nodes
18a3d84bb802 checks: add string list check for *-names properties
8fe94fd6f19f checks: add string list check
6c5730819604 checks: add a string check for 'label' property
a384191eba09 checks: fix sound-dai phandle with arg property check
b260c4f610c0 Fix ambiguous grammar for devicetree rule
fe667e382bac tests: Add some basic tests for the pci_bridge checks
7975f6422260 Fix widespread incorrect use of strneq(), replace with new strprefixeq()
fca296445eab Add strstarts() helper function
cc392f089007 tests: Check non-matching cases for fdt_node_check_compatible()
bba26a5291c8 livetree: avoid assertion of orphan phandles with overlays
c8f8194d76cc implement strnlen for systems that need it
c8b38f65fdec libfdt: Remove leading underscores from identifiers
3b62fdaebfe5 Remove leading underscores from identifiers
2d45d1c5c65e Replace FDT_VERSION() with stringify()
2e6fe5a107b5 Fix some errors in comments
b0ae9e4b0ceb tests: Correct warning in sw_tree1.c

Commit c8b38f65fdec upstream ("libfdt: Remove leading underscores from
identifiers") changed the multiple inclusion define protection, so the
kernel's libfdt_env.h needs the corresponding update.

Signed-off-by: Rob Herring <robh@kernel.org>