i.MX drivers update for 5.5: - Skip return check for those SCU firmware APIs that are defined as void function in firmware. - Use established serial_number attribute instead of custom one to show SoC's unique ID for i.MX8 SoC drivers. - Read i.MX8MQ SOC revision from TF-A which parses ROM and exposes the value through a SMC call. This improves the situation that SOC revision reports 'unknown' on some older revisions. - Add a check and warn on unexpected SCU RX to avoid potential stack corruption in imx-scu driver. - Fix a sparse warning in imx-scu-irq driver by adding missing header. - Remove an unneeded call to devm_of_platform_populate() from imx-dsp driver.