smbios: only look for a SYSINFO udevice if SYSINFO support is enabled

If SYSINFO support isn't enabled, it's a given that uclass_first_device
for UCLASS_SYSINFO will not find anything, therefore let's skip the test
entirely.

This allows to get rid of the following debug message that may be
confusing:

Cannot find uclass for id 118: please add the UCLASS_DRIVER() declaration for this UCLASS_... id

Signed-off-by: Quentin Schulz <quentin.schulz@cherry.de>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/lib/smbios.c b/lib/smbios.c
index b190b01..a822acd 100644
--- a/lib/smbios.c
+++ b/lib/smbios.c
@@ -571,7 +571,7 @@
 	int i;
 
 	ctx.node = ofnode_null();
-	if (IS_ENABLED(CONFIG_OF_CONTROL)) {
+	if (IS_ENABLED(CONFIG_OF_CONTROL) && CONFIG_IS_ENABLED(SYSINFO)) {
 		uclass_first_device(UCLASS_SYSINFO, &ctx.dev);
 		if (ctx.dev)
 			parent_node = dev_read_subnode(ctx.dev, "smbios");