fw_env: fix build error

The following error appears:

tools/env/fw_env.c:1149:25: error: lvalue required as unary ‘&’ operand
  rc = write(fd, &ENV_REDUND_OBSOLETE, sizeof(ENV_REDUND_OBSOLETE));

Fixes: d3716dd ("env: Rename the redundancy flags")

Signed-off-by: Pierre-Jean Texier <pjtexier@koncepto.io>
Tested-by: Joris Offouga <offougajoris@gmail.com>
Tested-by: Heiko Schocher <hs@denx.de>
Suggested-by: Heiko Schocher <hs@denx.de>
Acked-by: Joe Hershberger <joe.hershberger@ni.com>
diff --git a/tools/env/fw_env.c b/tools/env/fw_env.c
index 876bf2b..e2801f5 100644
--- a/tools/env/fw_env.c
+++ b/tools/env/fw_env.c
@@ -1135,6 +1135,7 @@
 {
 	int rc;
 	struct erase_info_user erase;
+	char tmp = ENV_REDUND_OBSOLETE;
 
 	erase.start = DEVOFFSET(dev);
 	erase.length = DEVESIZE(dev);
@@ -1146,7 +1147,7 @@
 		return rc;
 	}
 	ioctl(fd, MEMUNLOCK, &erase);
-	rc = write(fd, &ENV_REDUND_OBSOLETE, sizeof(ENV_REDUND_OBSOLETE));
+	rc = write(fd, &tmp, sizeof(tmp));
 	ioctl(fd, MEMLOCK, &erase);
 	if (rc < 0)
 		perror("Could not set obsolete flag");