env: Fix operation of 'make environ'

This was broken by the recent environment refactoring. Specifically:

$  make environ
scripts/Makefile.build:59: tools/environ/Makefile: No such file or directory
make[1]: *** No rule to make target 'tools/environ/Makefile'.  Stop.
make: *** [Makefile:1469: environ] Error 2

Fix this by updating the Makefile and adjusting the #include filesnames in
two C files.

Fixes: ec74f5f (Makefile: Rename 'env' target to 'environ')
Reported-by: Måns Rullgård <mans@mansr.com>
Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/tools/env/README b/tools/env/README
index 24e31bc..bc6e2c1 100644
--- a/tools/env/README
+++ b/tools/env/README
@@ -3,9 +3,9 @@
 the U-Boot's environment variables.
 
 In order to cross-compile fw_printenv, run
-    make CROSS_COMPILE=<your cross-compiler prefix> env
+    make CROSS_COMPILE=<your cross-compiler prefix> envtools
 in the root directory of the U-Boot distribution. For example,
-    make CROSS_COMPILE=arm-linux- env
+    make CROSS_COMPILE=arm-linux- envtools
 
 For the run-time utility configuration uncomment the line
 #define CONFIG_FILE  "/etc/fw_env.config"