gpio: 74x146: depend on DM_SPI

gpio: 74x146: depend on DM_SPI

Currently, Kconfig allows building CONFIG_DM_74X164 without
CONFIG_DM_SPI, which results in linker errors because this driver
actually uses dm_spi_* functions:

drivers/gpio/74x164_gpio.o: in function `gen_74x164_write_conf':
  undefined reference to `dm_spi_claim_bus'
  undefined reference to `dm_spi_xfer'
  undefined reference to `dm_spi_release_bus'

Signed-off-by: J. Neuschäfer <j.ne@posteo.net>