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>

tools/env/Makefile

@@ -26,7 +26,7 @@ include $(TOPDIR)/config.mk
 SRCS	:= $(obj)crc32.c  fw_env.c  fw_env_main.c
 HEADERS	:= fw_env.h
 
-CPPFLAGS := -Wall -DUSE_HOSTCC
+CPPFLAGS := -Wall -DUSE_HOSTCC -I$(SRCTREE)/include
 
 ifeq ($(MTD_VERSION),old)
 CPPFLAGS += -DMTD_OLD