Avoid code repetition in advk_pcie_rd_conf() by handling errors with
goto jump, as is customary in kernel.

Link: https://lore.kernel.org/r/20211005180952.6812-9-kabel@kernel.org
Fixes: 43f5c77b ("PCI: aardvark: Fix reporting CRS value")
Signed-off-by: NMarek Behún <kabel@kernel.org>
Signed-off-by: NLorenzo Pieralisi <lorenzo.pieralisi@arm.com>