Change in coreboot[master]: nb/intel/ironlake: Drop `pci_mmio_size`

[Nico Huber (Code Review)]

Attention is currently required from: Angel Pons, Arthur Heymans, Alexander Couzens, Patrick Rudolph.
Nico Huber has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/52070 )

Change subject: nb/intel/ironlake: Drop `pci_mmio_size`
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Patch Set 1: Code-Review+2

(1 comment)

Commit Message:

https://review.coreboot.org/c/coreboot/+/52070/comment/49f8a730_dbb00253 
PS1, Line 9: There's no good reason to use values smaller than 2 GiB here.
Well we know one reason: I increases available DRAM in 32-bit space.
If that's a good reason, I don't know. But we should at least mention
it (and maybe add that it was fragile / not bricking is better?).