PCI: pci-epf-test: Do not allocate next BARs memory if current BAR is 64Bit

It's useless to allocate memory for next BAR if the current BAR is a
64Bit BAR. Stop allocating memory for the next BAR, if the current
BARs flag indicates this is a 64Bit BAR.

Tested-by: Gustavo Pimentel <gustavo.pimentel@synopsys.com>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>