nanddump: make dumping read-only partitions work

Make dumping read-only partitions work by opening the device
O_RDONLY; otherwise the open() will fail with -EPERM.

Signed-off-by: Matt Reimer <mreimer@sdgsystems.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/miscutils/nandwrite.c b/miscutils/nandwrite.c
index 2ba6e3f..c636a5a 100644
--- a/miscutils/nandwrite.c
+++ b/miscutils/nandwrite.c
@@ -129,7 +129,7 @@
 		xmove_fd(tmp_fd, IS_NANDDUMP ? STDOUT_FILENO : STDIN_FILENO);
 	}
 
-	fd = xopen(argv[0], O_RDWR);
+	fd = xopen(argv[0], IS_NANDWRITE ? O_RDWR : O_RDONLY);
 	xioctl(fd, MEMGETINFO, &meminfo);
 
 	mtdoffset = xstrtou(opt_s, 0);