counter: 104-quad-8: Implement and utilize register structures

Reduce magic numbers and improve code readability by implementing and
utilizing named register data structures.

Link: https://lore.kernel.org/r/[email protected]/
Cc: Syed Nayyar Waris <[email protected]>
Tested-by: Fred Eckert <[email protected]>
Reviewed-by: Jonathan Cameron <[email protected]>
Signed-off-by: William Breathitt Gray <[email protected]>
Link: https://lore.kernel.org/r/285fdc7c03892251f50bdbf2c28c19998243a6a3.1657813472.git.william.gray@linaro.org
Signed-off-by: Greg Kroah-Hartman <[email protected]>