net: mana: Guard mana_remove against double invocation

In the Linux kernel, the following vulnerability has been resolved: net: mana: Guard mana_remove against double invocation If PM resume fails (e.g., mana_attach() returns an error), mana_probe() calls mana_remove(), which tears down the device and sets gd->gdma_context = NULL and gd->driver_data = NULL. However, a failed resume callback does not automatically unbind the driver. When the device is eventually unbound, mana_remove() is invoked a second time. Without a NULL check, it dereferences gc->dev with gc == NULL, causing a kernel panic. Add an early return if gdma_context or driver_data is NULL so the second invocation is harmless. Move the dev = gc->dev assignment after the guard so it cannot dereference NULL.