sandbox: eth-raw: do not close the console input

When the sandbox eth-raw device host_lo is removed this leads to closing
the console input.

Do not call close(0).

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/sandbox/cpu/os.c b/arch/sandbox/cpu/os.c
index e7ec892..c461fb0 100644
--- a/arch/sandbox/cpu/os.c
+++ b/arch/sandbox/cpu/os.c
@@ -86,7 +86,10 @@
 
 int os_close(int fd)
 {
-	return close(fd);
+	/* Do not close the console input */
+	if (fd)
+		return close(fd);
+	return -1;
 }
 
 int os_unlink(const char *pathname)