iio: st_sensors: don't always auto-enable I2C and SPI interface drivers

iio: st_sensors: don't always auto-enable I2C and SPI interface drivers

This patch makes I2C and SPI interface drivers for STMicroelectronics
sensor chips individually selectable via Kconfig.

The default is kept unchanged - I2C and SPI interface drivers are still
selected by default if the corresponding bus support is available.

However, the patch makes it possible to explicitly disable drivers
that are not needed for a particular target.

Signed-off-by: Nikita Yushchenko <nikita.yoush@cogentembedded.com>
Acked-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20220110152432.3799227-1-nikita.yoush@cogentembedded.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>