Fix Compilation Errors with 'tools/env/fw_printenv'

In the current top-of-tree, 1.3.3.-rc2, the optional tool
'tools/env/fw_printenv' fails to compile for two reasons:

1) The header watchdog.h cannot be found.
2) The header zlib.h is picked up from the tool chain rather than the
   project causing a prototype conflict for crc32.

This patch addresses both of these issues.

Platforms Tested On:
- AMCC "Kilauea"

Signed-off-by: Grant Erickson <gerickson@nuovations.com>
diff --git a/lib_generic/crc32.c b/lib_generic/crc32.c
index 64f66ed..83d1d1d 100644
--- a/lib_generic/crc32.c
+++ b/lib_generic/crc32.c
@@ -14,7 +14,9 @@
 #include <stdint.h>
 #endif
 
+#if defined(CONFIG_HW_WATCHDOG) || defined(CONFIG_WATCHDOG)
 #include <watchdog.h>
+#endif
 #include "zlib.h"
 
 #define local static