mfd: lpc_sch: Reduce duplicate code and improve manageability

This patch refactors the driver to use helper functions instead of
copy'n'pasted pieces of code.

It also introduces an additional struct to hold a chipset info. The chipset
info will be used to store features that are supported by specific processor or
chipset. LPC_SCH supports SMBUS, GPIO and WDT features. As this code base might
expand further to support more processors, this implementation will help to
keep code base clean and manageable.

The patch is partially based on the work done by Chang Rebecca Swee Fun.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Tested-by: Chang Rebecca Swee Fun <rebecca.swee.fun.chang@intel.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>