mfd: twl6040: Drop twl6040_platform_data and associated definitions

As of df04b624 ("mfd: twl6040: Remove support for legacy (pdata)
mode") the driver no longer references the platform data, so we can drop
its definition, as well as definitions of related structures.

Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Lee Jones <lee@kernel.org>
Link: https://lore.kernel.org/r/20220926054421.1546436-5-dmitry.torokhov@gmail.com