net: ngbe: fix NULL pointer dereference in non-MSI-X interrupt enabling

In the Linux kernel, the following vulnerability has been resolved: net: ngbe: fix NULL pointer dereference in non-MSI-X interrupt enabling In non-MSI-X mode (such as legacy INTx or single MSI), wx->msix_entry is not allocated or initialized. Calling NGBE_INTR_MISC(wx) dereferences wx->msix_entry->entry, leading to a NULL pointer dereference crash. This issue was introduced by fixing the IRQ vector when the number of VFs is 7. Fix the issue by explicitly checking `pdev->msix_enabled` to determine the correct vector index. Additionally, as a side fix, set the interrupt mask to BIT(0) for the non-MSI-X fallback. In MSI/INTx mode, the MISC and queue interrupts share vector 0, and the WX_PX_MISC_IVAR register is only valid in the MSI-X case. Thus, BIT(0) is the correct mask for the miscellaneous cause when MSI-X is disabled.