pmic: Extend PMIC framework to support multiple instances of PMIC devices

The PMIC framework has been extended to support multiple instances of
the variety of devices responsible for power management.
This change allows supporting of e.g. fuel gauge, charger, MUIC (Micro USB
Interface Circuit).
Power related includes have been moved to ./include/power directory.
This is a first of a series of patches - in the future "pmic" will be
replaced with "power".

Two important issues:
1. The PMIC needs to be initialized just after malloc is configured
2. It uses list to hold information about available PMIC devices

Signed-off-by: Lukasz Majewski <l.majewski@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Cc: Stefano Babic <sbabic@denx.de>