PCI: aardvark: Indicate error in 'val' when config read fails

PCI: aardvark: Indicate error in 'val' when config read fails

commit df7a57322f2fd77ddd441b4438dde2512d3ba149 upstream.

Most callers of config read do not check for return value. But most of the
ones that do, checks for error indication in 'val' variable.

This patch updates error handling in advk_pcie_rd_conf() function. If PIO
transfer fails then 'val' variable is set to 0xffffffff which indicates
failture.

Link: https://lore.kernel.org/r/20200528162604.GA323482@bjorn-Precision-5520
Link: https://lore.kernel.org/r/20200601130315.18895-1-pali@kernel.org
Reported-by: Bjorn Helgaas <helgaas@kernel.org>
Signed-off-by: Pali Rohár <pali@kernel.org>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>