regmap: Prepare LZO cache for variable block sizes

Give regcache_lzo_block_count() a copy of the map so that when we decide
we want to make the LZO cache more controllable we can more easily do so.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Acked-by: Dimitris Papastamos <dp@opensource.wolfsonmicro.com>