flashchips: Mark GigaDevice GD25Q128C as tested

As per Tomasz Walach on the mailing list.

Change-Id: Ib0d7485c7221f92ec13995c58065a48e08f57cd8
Signed-off-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-on: https://review.coreboot.org/28819
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Nico Huber <nico.h@gmx.de>
diff --git a/flashchips.c b/flashchips.c
index a70d953..45a392f 100644
--- a/flashchips.c
+++ b/flashchips.c
@@ -6398,7 +6398,7 @@
 		/* OTP: 1536B total; read 0x48; write 0x42, erase 0x44 */
 		/* QPI: enable 0x38, disable 0xFF */
 		.feature_bits	= FEATURE_WRSR_WREN | FEATURE_OTP | FEATURE_QPI,
-		.tested		= TEST_UNTESTED,
+		.tested		= TEST_OK_PREW,
 		.probe		= probe_spi_rdid,
 		.probe_timing	= TIMING_ZERO,
 		.block_erasers	=