sandbox: Allow ethernet bootdevs to be disabled for tests

Most tests don't want these and can create a lot of noise. Add a way to
disable them. Use that in tests, with a flag provided to enable them for
tests that need this feature.

Signed-off-by: Simon Glass <sjg@chromium.org>

include/test/test.h

@@ -71,6 +71,7 @@ enum {
 	 * since it cannot access the flags.
 	 */
 	UT_TESTF_MANUAL		= BIT(8),
+	UT_TESTF_ETH_BOOTDEV	= BIT(9),	/* enable Ethernet bootdevs */
 };
 
 /**
@@ -194,4 +195,15 @@ static inline bool test_eth_enabled(void)
 	return enabled;
 }
 
+/* Allow ethernet bootdev to be ignored for testing purposes */
+static inline bool test_eth_bootdev_enabled(void)
+{
+	bool enabled = true;
+
+#ifdef CONFIG_SANDBOX
+	enabled = sandbox_eth_enabled();
+#endif
+	return enabled;
+}
+
 #endif /* __TEST_TEST_H */