PCI: dwc: ep: Move dw_pcie_ep_find_ext_capability()

PCI: dwc: ep: Move dw_pcie_ep_find_ext_capability()

Move dw_pcie_ep_find_ext_capability() so that it is located next to
dw_pcie_ep_find_capability().

Additionally, a follow-up commit requires this to be defined earlier
in order to avoid a forward declaration.

Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Signed-off-by: Niklas Cassel <cassel@kernel.org>
Link: https://lore.kernel.org/r/20250131182949.465530-12-cassel@kernel.org
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Signed-off-by: Krzysztof Wilczyński <kwilczynski@kernel.org>