dtc/libfdt: install missing header

Previously, only two headers were installed: libfdt.h and fdt.h.
But libfdt.h also #includes libfdt_env.h, which was not installed.

Install this missing header too.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Acked-by: David Gibson <david@gibson.dropbear.id.au>
(cherry picked from commit 8716901d2215a314504b7df6282aedfcf89da1ea)

BUG=none
TEST=sudo emerge dtc

See that usr/include/libfdt_env.h now exists

Change-Id: I89548d85a94e0eb96364b287398f1745cee819e7
Reviewed-on: https://gerrit.chromium.org/gerrit/43381
Reviewed-by: Mike Frysinger <vapier@chromium.org>
Reviewed-by: David Hendricks <dhendrix@chromium.org>
Commit-Queue: David Hendricks <dhendrix@chromium.org>
Tested-by: David Hendricks <dhendrix@chromium.org>
diff --git a/libfdt/Makefile.libfdt b/libfdt/Makefile.libfdt
index 4366627..91126c0 100644
--- a/libfdt/Makefile.libfdt
+++ b/libfdt/Makefile.libfdt
@@ -4,7 +4,7 @@
 # be easily embeddable into other systems of Makefiles.
 #
 LIBFDT_soname = libfdt.$(SHAREDLIB_EXT).1
-LIBFDT_INCLUDES = fdt.h libfdt.h
+LIBFDT_INCLUDES = fdt.h libfdt.h libfdt_env.h
 LIBFDT_VERSION = version.lds
 LIBFDT_SRCS = fdt.c fdt_ro.c fdt_wip.c fdt_sw.c fdt_rw.c fdt_strerror.c fdt_empty_tree.c
 LIBFDT_OBJS = $(LIBFDT_SRCS:%.c=%.o)