crc32: Use the crc.h header for crc functions

Drop inclusion of crc.h in common.h and use the correct header directly
instead.

With this we can drop the conflicting definition in fw_env.h and rely on
the crc.h header, which is already included.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Tom Rini <trini@konsulko.com>
diff --git a/env/flash.c b/env/flash.c
index b94ed2b..b487e67 100644
--- a/env/flash.c
+++ b/env/flash.c
@@ -17,6 +17,7 @@
 #include <malloc.h>
 #include <search.h>
 #include <errno.h>
+#include <u-boot/crc.h>
 
 DECLARE_GLOBAL_DATA_PTR;