[flashrom] Mark SST39SF040 as TEST_OK_PREW

[David Borg]

Mark the SST39SF040 as tested ok for all operations.

Index: flashchips.c
===================================================================
--- flashchips.c	(revision 1145)
+++ flashchips.c	(working copy)
@@ -5183,7 +5183,7 @@
 		.total_size	= 512,
 		.page_size	= 4096,
 		.feature_bits	= FEATURE_EITHER_RESET,
-		.tested		= TEST_UNTESTED,
+		.tested		= TEST_OK_PREW,
 		.probe		= probe_jedec,
 		.probe_timing	= 1,			/* 150 ns */
 		.block_erasers	=