WIP: Add wrappers for qfprom access via syscon

Syscon fits very well to access qfprom. This also means drivers which needs to
access qfprom have to talk to syscon and get regmap, offset, size and then do
regmap reads. This will be kinda redone in every driver. Having a wrapper for
this would avoid lot of code duplications and also provide a higher level and
user friendly apis for qfprom. This patch attempt to provide such wrappers.
This wrappers are easy way to use syscon for qfprom purposes.

Advantages of this approch is:

- driver need not have hardcoded qfprom offsets or have soc specific
  compatible strings to determine the offset.
- access multiple qfprom resources which is kinda tricky with standard
  syscon.
- no code duplication.
- light weight, single call.
- not a platform device driver level binding.

Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>