IIO_ST_SENSORS_CORE select IIO_ST_SENSORS_I2C
unconditionally, if REGMAP_I2C is not set, build fails

drivers/iio/common/st_sensors/st_sensors_i2c.o: In function `st_sensors_i2c_configure':
st_sensors_i2c.c:(.text+0x58): undefined reference to `__devm_regmap_init_i2c'

This patch selects REGMAP_I2C to fix it.
IIO_ST_SENSORS_SPI is similar to SPI issue.
Reported-by: Hulk Robot <hulkci@huawei.com>
Fixes: 062809ef ("iio: make st_sensors drivers use regmap")
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>