env: move extern default_environment[] to environment.h

Extract all extern declarations for default_environment[] out of c files
into the environment.h header.

Signed-off-by: Igor Grinberg <grinberg@compulab.co.il>
Cc: Stefan Roese <sr@denx.de>
Acked-by: Stefan Roese <sr@denx.de>
diff --git a/include/environment.h b/include/environment.h
index 2c8c4f1..20775da 100644
--- a/include/environment.h
+++ b/include/environment.h
@@ -154,6 +154,8 @@
 	unsigned char	data[ENV_SIZE]; /* Environment data		*/
 } env_t;
 
+extern const unsigned char default_environment[];
+
 #ifndef DO_DEPS_ONLY
 
 #include <search.h>