Valid values for function are:
- mdio, mi2s, pdm, ssbi, spmi, audio_pcm, gsbi1, gsbi2, gsbi4, gsbi5,
+ mdio, mi2s, pdm, ssbi, spmi, audio_pcm, gpio, gsbi1, gsbi2, gsbi4, gsbi5,
gsbi5_spi_cs1, gsbi5_spi_cs2, gsbi5_spi_cs3, gsbi6, gsbi7, nss_spi, sdc1,
spdif, nand, tsif1, tsif2, usb_fs_n, usb_fs, usb2_hsic, rgmii2, sata,
pcie1_rst, pcie1_prsnt, pcie1_pwren_n, pcie1_pwren, pcie1_pwrflt,