env: Move env_get() to env.h

Move env_get() over to the new header file.

Acked-by: Joe Hershberger <joe.hershberger@ni.com>
Signed-off-by: Simon Glass <sjg@chromium.org>

board/BuS/eb_cpu5282/eb_cpu5282.c

@@ -11,6 +11,7 @@
 #include <command.h>
 #include "asm/m5282.h"
 #include <bmp_layout.h>
+#include <env.h>
 #include <status_led.h>
 #include <bus_vcxk.h>