Check the return value of device_create_bin_file in pci_create_bus and
unwind if necessary. Don't propagate error to caller, as failure to create
these files shouldn't prevent PCI from being initialised. Instead, just
log a warning.

Cc: Sven Wegener <sven.wegener@stealer.net>
Cc: Michael Ellerman <michael@ellerman.id.au>
Cc: Matthew Wilcox <matthew@wil.cx>
Signed-off-by: Simon Horman <horms@verge.net.au>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>