PCI: Align checking of syscall user config accessors

After 34e32072 ("PCI: handle positive error codes"),
pci_user_read_config_*() and pci_user_write_config_*() return 0 or negative
errno values, not PCIBIOS_* values like PCIBIOS_SUCCESSFUL or
PCIBIOS_BAD_REGISTER_NUMBER.

Remove comparisons with PCIBIOS_SUCCESSFUL and check only for non-zero.  It
happens that PCIBIOS_SUCCESSFUL is zero, so this is not a functional
change, but it aligns this code with the user accessors.

[bhelgaas: commit log]
Fixes: 34e32072 ("PCI: handle positive error codes")
Link: https://lore.kernel.org/r/f1220314-e518-1e18-bf94-8e6f8c703758@gmail.com


Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>