Change the status of the SST49LF020A to TEST_OK_PREW

I tested it on the Wyse Winterm S50 see attached test results.

Corresponding to flashrom svn r730.
Signed-off-by: Nils Jacobs <njacobs8@hetnet.nl>
Acked-by: Carl-Daniel Hailfinger <c-d.hailfinger.devel.2006@gmx.net>

flashchips.c

@@ -2244,7 +2244,7 @@ struct flashchip flashchips[] = {
 		.model_id	= SST_49LF020A,
 		.total_size	= 256,
 		.page_size	= 4 * 1024,
-		.tested		= TEST_UNTESTED,
+		.tested		= TEST_OK_PREW,
 		.probe		= probe_jedec,
 		.probe_timing	= 1,			/* 150 ns */ 
 		.erase		= erase_49lf040,