fs: exfat: Demote filesystem detection failure message to debug()

Demote "exFAT file system is not found" message to debug(). This is
printed when U-Boot attempts to auto-detect the filesystem via generic
filesystem API by attempting to mount the device, and fails to do so
because there is another filesystem in place. The libexfat-fuse code
prints this an error, which interferes with 'test_gpt' test. Demote
the message to debug().

Reviewed-by: Tom Rini <trini@konsulko.com>
Signed-off-by: Marek Vasut <marex@denx.de>
diff --git a/fs/exfat/mount.c b/fs/exfat/mount.c
index c17a847..0ff297a 100644
--- a/fs/exfat/mount.c
+++ b/fs/exfat/mount.c
@@ -226,7 +226,12 @@
 	}
 	if (memcmp(ef->sb->oem_name, "EXFAT   ", 8) != 0)
 	{
-		exfat_error("exFAT file system is not found");
+#ifndef __UBOOT__
+		exfat_error(
+#else
+		exfat_debug(
+#endif
+		"exFAT file system is not found");
 		exfat_free(ef);
 		return -EIO;
 	}