x86/PCI: Add support for the SiS85C497 PIRQ router

The SiS 85C496/497 486 Green PC VESA/ISA/PCI Chipset has support for PCI 
steering and the ELCR register implemented.  These features are handled 
by the SiS85C497 AT Bus Controller & Megacell (ATM) ISA bridge, however 
the device is wired as a peer bridge directly to the host bus and has 
its PCI configuration registers decoded at addresses 0x80-0xff by the 
accompanying SiS85C496 PCI & CPU Memory Controller (PCM) host bridge[1].  
Therefore we need to match on the host bridge's vendor and device ID.

Like with the SiS85C503 PIRQ router handle link value ranges of 1-4 and 
0xc0-0xc3, corresponding respectively to PIRQ line numbers counted from 
1 and link register PCI configuration space addresses.

References:

[1]  "486 Green PC VESA/ISA/PCI Chipset, SiS 85C496/497", Rev 3.0,
     Silicon Integrated Systems Corp., July 1995, Part IV, Section 3. 
     "PCI Configuration Space Registers (00h ~ FFh)", p. 114

Signed-off-by: Maciej W. Rozycki <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Tested-by: Nikolai Zhubr <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

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