iwlwifi: convert flat SAR profile table to a struct version

The SAR profiles have been stored in single-dimension arrays and the
access has been done via a single index.  We will soon need to support
different revisions of this table, which will make the flat array even
harder to handle.  To prepare for that, convert the single-dimension
array to a struct with substructures.

Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Link: https://lore.kernel.org/r/iwlwifi.20210805130823.01530088097f.I903c236a574c7e4c0fc4db101fc39c0f5415ca43@changeid
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>