flashchips: Mark GigaDevice GD25Q512 as tested

As reported by `nvflash` on IRC.

Change-Id: Id3928e3790ddac34645959535e646d552ce5328e
Signed-off-by: Nico Huber <nico.h@gmx.de>
Reviewed-on: https://review.coreboot.org/28209
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Stefan Tauner <stefan.tauner@gmx.at>
diff --git a/flashchips.c b/flashchips.c
index 464e9b5..1a73ba4 100644
--- a/flashchips.c
+++ b/flashchips.c
@@ -6054,7 +6054,7 @@
 		.total_size	= 64,
 		.page_size	= 256,
 		.feature_bits	= FEATURE_WRSR_WREN,
-		.tested		= TEST_UNTESTED,
+		.tested		= TEST_OK_PREW,
 		.probe		= probe_spi_rdid,
 		.probe_timing	= TIMING_ZERO,
 		.block_erasers	= {