Set default CDI spec permissions to 644

Although the nvidia-ctk cdi generate command generates
specs with 644 permissions, the nvidia-ctk cdi transform
commands do not. This change sets the default permissions
to 600 instead of 644.

Signed-off-by: Evan Lezar <elezar@nvidia.com>

pkg/nvcdi/spec/builder.go

@@ -67,7 +67,7 @@ func newBuilder(opts ...Option) *builder {
 		s.format = FormatYAML
 	}
 	if s.permissions == 0 {
-		s.permissions = 0600
+		s.permissions = 0644
 	}
 	return s
 }