PCI: Fix INTC comment typo for pci_swizzle_interrupt_pin()

The INTx pin should be INIT[ABCD].  Fix the typo "3=INTC".

Signed-off-by: Wang Sheng-Hui <shhuiw@gmail.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>