flashchips.c: mark MX25U25635F as TESTED_OK_PREW

The chip was marked as TESTED_OK_PREW in the cros tree by
`commit 419e32ae457cc36b03757b89471a7ce3770e9611`.

Quoting from the original commit message:
> TEST=Tested writes using Servo

Change-Id: Id7f44a41d6b2c397f1ce2e345f8ab44e95e4cfa2
Signed-off-by: Nikolai Artemiev <nartemiev@google.com>
Reviewed-on: https://review.coreboot.org/c/flashrom/+/51736
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-by: Edward O'Callaghan <quasisec@chromium.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
diff --git a/flashchips.c b/flashchips.c
index 2f87515..5b328f8 100644
--- a/flashchips.c
+++ b/flashchips.c
@@ -9326,7 +9326,7 @@
 		.page_size	= 256,
 		/* OTP: 512B total; enter 0xB1, exit 0xC1 */
 		.feature_bits	= FEATURE_WRSR_WREN | FEATURE_OTP | FEATURE_QPI | FEATURE_4BA,
-		.tested		= TEST_OK_PR,
+		.tested		= TEST_OK_PREW,
 		.probe		= probe_spi_rdid,
 		.probe_timing	= TIMING_ZERO,
 		.block_erasers	=