fs: littlefs: sample: Generate fname[12] strings after mount

The littlefs_mount() function sets the mount point for block devices,
so fname[12] shall be generated after calling it.

Signed-off-by: Lukasz Majewski <lukma@denx.de>
diff --git a/samples/subsys/fs/littlefs/src/main.c b/samples/subsys/fs/littlefs/src/main.c
index 714f21e..95f27b2 100644
--- a/samples/subsys/fs/littlefs/src/main.c
+++ b/samples/subsys/fs/littlefs/src/main.c
@@ -338,14 +338,14 @@
 
 	LOG_PRINTK("Sample program to r/w files on littlefs\n");
 
-	snprintf(fname1, sizeof(fname1), "%s/boot_count", mp->mnt_point);
-	snprintf(fname2, sizeof(fname2), "%s/pattern.bin", mp->mnt_point);
-
 	rc = littlefs_mount(mp);
 	if (rc < 0) {
 		return;
 	}
 
+	snprintf(fname1, sizeof(fname1), "%s/boot_count", mp->mnt_point);
+	snprintf(fname2, sizeof(fname2), "%s/pattern.bin", mp->mnt_point);
+
 	rc = fs_statvfs(mp->mnt_point, &sbuf);
 	if (rc < 0) {
 		LOG_PRINTK("FAIL: statvfs: %d\n", rc);