soc/intel/xeon_sp/cpx: correct GSI bases for IO APICs

soc/intel/xeon_sp/cpx: correct GSI bases for IO APICs

With CPX-SP FSP, PCH IOAPIC handles the first 120(0x78) GSIs. Correct
the coreboot assignment of GSIs for IO APICs.

Without this patch, there are following target OS boot messages:
[    1.098771] IOAPIC[0]: apic_id 8, version 32, address 0xfec00000, GSI 0-119
[    1.099159] GSI range [24-31] for new IOAPIC conflicts with GSI[0-119]

After this patch, the boot messages are:
[    0.399498] IOAPIC[0]: apic_id 8, version 32, address 0xfec00000, GSI 0-119
[    0.399848] IOAPIC[1]: apic_id 9, version 32, address 0xfec01000, GSI 120-127

Also without this patch, there is boot stability issue. About one in
20 reboots, the target OS fails to boot with following failure:
[    4.325795] mce: [Hardware Error]: Machine check events logged
[    4.326597] mce: [Hardware Error]: CPU 0: Machine Check: 0 Bank 9: ee2000000003110a
[    4.327594] mce: [Hardware Error]: TSC 0 ADDR fe9e0000 MISC 228aa040101086
[    4.328596] mce: [Hardware Error]: PROCESSOR 0:5065b TIME 1601443875 SOCKET 0 APIC 0 microcode 700001d

The MCE error happens in bank 9. The Model specific error code
shows it is about SAD_ERR_WB_TO_MMIO error (doc 604926), which means
something goes wrong when cache write back to mmio. It is a generic
transaction type error in level 2.

Signed-off-by: Jonathan Zhang <jonzhang@fb.com>
Change-Id: I45e941591300dad6d583a6dcb41f45e984753c07
Reviewed-on: https://review.coreboot.org/c/coreboot/+/45941
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-by: Christian Walter <christian.walter@9elements.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>