regmap: regcache: Fixup locking for custom lock callbacks

The parameter passed to the regmap lock/unlock callbacks needs to be
map->lock_arg, regcache passes just map. This works fine in the case that no
custom locking callbacks are used since in this case map->lock_arg equals map,
but will break when custom locking callbacks are used. The issue was introduced
in commit 0d4529c5("regmap: make lock/unlock functions customizable") and is
fixed by this patch.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>