ssb: SPROM: extract each core power info

We already extract some basic info but it's incomplete, reads info
about the first core only. Used data structure doesn't allow easy
adding of more cores.
This patch adds new struct and array for storing power info. The plan
is to: switch all extractors (including the ones using NVRAM) to new
struct, switch drivers, then deprecate and finally drop old SSB fields.

Signed-off-by: Rafał Miłecki <zajec5@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>