libpci: djgpp: Handle Windows NTVDM zero error codes

Windows NTVDM DPMI host clears the AX register for unsupported DPMI calls.
So handle zero error code as ENOSYS instead of default case EACCES.

libpci: Add DJGPP physmem support for PCIe ECAM access

It requires either Device Mapping support on DPMI host or Physical Address
Mapping support together with support for changing DS descriptor lim

libpci: Add DJGPP physmem support for PCIe ECAM access

It requires either Device Mapping support on DPMI host or Physical Address
Mapping support together with support for changing DS descriptor limit to
maximal size 4 GB which enables address wrapping and so access to addresses
below the process base address.

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