misc: pci_endpoint_test: Fix pci_endpoint_test_bars_read_bar() error handling

misc: pci_endpoint_test: Fix pci_endpoint_test_bars_read_bar() error handling

Commit f26d37ee9bda ("misc: pci_endpoint_test: Fix IOCTL return value")
changed the return value of pci_endpoint_test_bars_read_bar() from false
to -EINVAL on error, however, it failed to update the error handling.

Fixes: f26d37ee9bda ("misc: pci_endpoint_test: Fix IOCTL return value")
Signed-off-by: Niklas Cassel <cassel@kernel.org>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Link: https://lore.kernel.org/r/20250204110640.570823-2-cassel@kernel.org
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Signed-off-by: Krzysztof Wilczyński <kwilczynski@kernel.org>