counter: 104-quad-8: Utilize bitfield access macros

The 104-QUAD-8 features several registers with various bitfields.
Utilize bitfield access macros such as u8_get_bits() and
u8_encode_bits() to make the code easier to read and the intent clearer.
Suggested-by: Jonathan Cameron <jic23@kernel.org>
Link: https://lore.kernel.org/r/7cea5ad049c75d8d1c6f25e288aa743a8d2a25d8.1681753140.git.william.gray@linaro.org/Signed-off-by: William Breathitt Gray <william.gray@linaro.org>