PCI: dwc: endpoint: Fix advertised resizable BAR size

PCI: dwc: endpoint: Fix advertised resizable BAR size

The commit message in commit fc9a77040b04 ("PCI: designware-ep: Configure
Resizable BAR cap to advertise the smallest size") claims that it modifies
the Resizable BAR capability to only advertise support for 1 MB size BARs.

However, the commit writes all zeroes to PCI_REBAR_CAP (the register which
contains the possible BAR sizes that a BAR be resized to).

According to the spec, it is illegal to not have a bit set in
PCI_REBAR_CAP, and 1 MB is the smallest size allowed.

Set bit 4 in PCI_REBAR_CAP, so that we actually advertise support for a
1 MB BAR size.

Before:
        Capabilities: [2e8 v1] Physical Resizable BAR
                BAR 0: current size: 1MB
                BAR 1: current size: 1MB
                BAR 2: current size: 1MB
                BAR 3: current size: 1MB
                BAR 4: current size: 1MB
                BAR 5: current size: 1MB
After:
        Capabilities: [2e8 v1] Physical Resizable BAR
                BAR 0: current size: 1MB, supported: 1MB
                BAR 1: current size: 1MB, supported: 1MB
                BAR 2: current size: 1MB, supported: 1MB
                BAR 3: current size: 1MB, supported: 1MB
                BAR 4: current size: 1MB, supported: 1MB
                BAR 5: current size: 1MB, supported: 1MB

Fixes: fc9a77040b04 ("PCI: designware-ep: Configure Resizable BAR cap to advertise the smallest size")
Link: https://lore.kernel.org/linux-pci/20240307111520.3303774-1-cassel@kernel.org
Signed-off-by: Niklas Cassel <cassel@kernel.org>
Signed-off-by: Krzysztof Wilczyński <kwilczynski@kernel.org>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Cc: <stable@vger.kernel.org> # 5.2