flashchips.c: Mark MT25QU256 as tested

As reported by Charles Parent on the mailing list.

Change-Id: I9d8b0038673185103ba08c9797ff94f2f7639d6c
Signed-off-by: Angel Pons <th3fanbus@gmail.com>
Original-Reviewed-on: https://review.coreboot.org/c/flashrom/+/62664
Original-Reviewed-by: Nico Huber <nico.h@gmx.de>
Original-Reviewed-by: Thomas Heijligen <src@posteo.de>
Original-Reviewed-by: Felix Singer <felixsinger@posteo.net>
Reviewed-on: https://review.coreboot.org/c/flashrom-stable/+/70998
Reviewed-by: Nico Huber <nico.h@gmx.de>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
diff --git a/flashchips.c b/flashchips.c
index b8ea6c7..dbdbaa1 100644
--- a/flashchips.c
+++ b/flashchips.c
@@ -11780,7 +11780,7 @@
 		/* supports SFDP */
 		/* OTP: 64B total; read 0x4B, write 0x42 */
 		.feature_bits	= FEATURE_WRSR_WREN | FEATURE_OTP | FEATURE_4BA_WREN,
-		.tested		= TEST_UNTESTED,
+		.tested		= TEST_OK_PREW,
 		.probe		= probe_spi_rdid,
 		.probe_timing	= TIMING_ZERO,
 		.block_erasers	=