counter: 104-quad-8: Migrate to the regmap API

The regmap API supports IO port accessors so we can take advantage of
regmap abstractions rather than handling access to the device registers
directly in the driver. With regmap we get boundary checks, read-write
permissions, operation synchronization locks, and more for free. Most
important of all, rather than rolling our own we utilize implementations
that are known to work and gain from any future improvements and fixes
that come.

Suggested-by: Andy Shevchenko <[email protected]>
Link: https://lore.kernel.org/r/1f1f7920d2be94aedb6fdf49f429fe6137c8cb24.1681753140.git.william.gray@linaro.org/
Signed-off-by: William Breathitt Gray <[email protected]>

Author: William Breathitt Gray