PCI: imx6: Change imx_pcie_deassert_core_reset() return type to void

PCI: imx6: Change imx_pcie_deassert_core_reset() return type to void

The function imx_pcie_deassert_core_reset() always returns 0 and the
return value is not used meaningfully by its callers.

Change the return type from int to void to simplify the code and
remove unnecessary error handling paths. No functional change intended.

Signed-off-by: Sherry Sun <sherry.sun@nxp.com>
Signed-off-by: Manivannan Sadhasivam <mani@kernel.org>
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Reviewed-by: Richard Zhu <hongxing.zhu@nxp.com>
Link: https://patch.msgid.link/20260306021247.991976-1-sherry.sun@nxp.com