o introduce PCIE_REGMAX and use it instead of ad-hoc constant
o where 'reg' parameter/variable is not already unsigned, cast it to
unsigned before comparison with maximum value to cut off negative
values
o use PCI_SLOTMAX in several places where 31 or 32 were explicitly used
o drop redundant check of 'bytes' in i386 pciereg_cfgread() - valid
values are already checked in the subsequent switch
Reviewed by: jhb
MFC after: 1 week
1e908511f8