regmap: mmio: Get rid of broken 64-bit IO

regmap: mmio: Get rid of broken 64-bit IO

The current implementation, besides having no active users, is broken
by design of regmap. For 64-bit IO we need to supply 64-bit value,
otherwise there is no way to handle upper 32 bits in 64-bit register.

Hence, remove the broken IO accessors for good and wait for real user
that can fix entire regmap API for that.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: William Breathitt Gray <william.gray@linaro.org>
Link: https://lore.kernel.org/r/20220808203401.35153-3-andriy.shevchenko@linux.intel.com
Signed-off-by: Mark Brown <broonie@kernel.org>