PCI: designware-ep: Remove static keyword from dw_pcie_ep_reset_bar()

Remove the static keyword from dw_pcie_ep_reset_bar() so that
pci-dra7xx.c does not need its own copy of dw_pcie_ep_reset_bar().

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