mfd: qcom-spmi-pmic: read fab id on supported PMICs

mfd: qcom-spmi-pmic: read fab id on supported PMICs

The PMI8998 and PM660 expose the fab_id, this is needed by drivers like
the RRADC to calibrate ADC values.

Signed-off-by: Caleb Connolly <caleb.connolly@linaro.org>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Tested-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Acked-by: Lee Jones <lee.jones@linaro.org>
Link: https://lore.kernel.org/r/20220429220904.137297-4-caleb.connolly@linaro.org
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>