mfd: Rohm PMICs: Use platform_device_id to match MFD sub-devices

Thanks to Stephen Boyd I today learned we can use platform_device_id
to do device and module matching for MFD sub-devices!

Do device matching using the platform_device_id instead of using
explicit module_aliases to load modules and custom parent-data field
to do module loading and sub-device matching.

Cc: Stephen Boyd <sboyd@kernel.org>
Signed-off-by: Matti Vaittinen <matti.vaittinen@fi.rohmeurope.com>
Acked-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>