libfdt: move headers to <linux/libfdt.h> and <linux/libfdt_env.h>

Thomas reported U-Boot failed to build host tools if libfdt-devel
package is installed because tools include libfdt headers from
/usr/include/ instead of using internal ones.

This commit moves the header code:
  include/libfdt.h         -> include/linux/libfdt.h
  include/libfdt_env.h     -> include/linux/libfdt_env.h

and replaces include directives:
  #include <libfdt.h>      -> #include <linux/libfdt.h>
  #include <libfdt_env.h>  -> #include <linux/libfdt_env.h>

Reported-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
diff --git a/common/spl/spl_fat.c b/common/spl/spl_fat.c
index 60b85f0..59a85a9 100644
--- a/common/spl/spl_fat.c
+++ b/common/spl/spl_fat.c
@@ -15,7 +15,7 @@
 #include <fat.h>
 #include <errno.h>
 #include <image.h>
-#include <libfdt.h>
+#include <linux/libfdt.h>
 
 static int fat_registered;
 
diff --git a/common/spl/spl_fit.c b/common/spl/spl_fit.c
index cc07fbc..b705d03 100644
--- a/common/spl/spl_fit.c
+++ b/common/spl/spl_fit.c
@@ -8,7 +8,7 @@
 #include <common.h>
 #include <errno.h>
 #include <image.h>
-#include <libfdt.h>
+#include <linux/libfdt.h>
 #include <spl.h>
 
 #ifndef CONFIG_SYS_BOOTM_LEN
diff --git a/common/spl/spl_nand.c b/common/spl/spl_nand.c
index cd39f9b..d075985 100644
--- a/common/spl/spl_nand.c
+++ b/common/spl/spl_nand.c
@@ -9,7 +9,7 @@
 #include <spl.h>
 #include <asm/io.h>
 #include <nand.h>
-#include <libfdt_env.h>
+#include <linux/libfdt_env.h>
 #include <fdt.h>
 
 #if defined(CONFIG_SPL_NAND_RAW_ONLY)
diff --git a/common/spl/spl_net.c b/common/spl/spl_net.c
index ef13145..50d0247 100644
--- a/common/spl/spl_net.c
+++ b/common/spl/spl_net.c
@@ -11,7 +11,7 @@
 #include <errno.h>
 #include <spl.h>
 #include <net.h>
-#include <libfdt.h>
+#include <linux/libfdt.h>
 
 DECLARE_GLOBAL_DATA_PTR;
 
diff --git a/common/spl/spl_ram.c b/common/spl/spl_ram.c
index fa8c768..d9db9f3 100644
--- a/common/spl/spl_ram.c
+++ b/common/spl/spl_ram.c
@@ -14,7 +14,7 @@
 #include <binman_sym.h>
 #include <mapmem.h>
 #include <spl.h>
-#include <libfdt.h>
+#include <linux/libfdt.h>
 
 #ifndef CONFIG_SPL_LOAD_FIT_ADDRESS
 # define CONFIG_SPL_LOAD_FIT_ADDRESS	0
diff --git a/common/spl/spl_ymodem.c b/common/spl/spl_ymodem.c
index ff8085b..4ab3dcd 100644
--- a/common/spl/spl_ymodem.c
+++ b/common/spl/spl_ymodem.c
@@ -14,7 +14,7 @@
 #include <xyzModem.h>
 #include <asm/u-boot.h>
 #include <asm/utils.h>
-#include <libfdt.h>
+#include <linux/libfdt.h>
 
 #define BUF_SIZE 1024