mfd: ab8500: Remove non-existent configuration "#ifdef CONFIG_AB8500_DEBUG"

The CONFIG_AB8500_DEBUG has been deleted in:

  3d4d1266 ("mfd: ab8500: Drop debugfs module")

The condition "#ifdef CONFIG_AB8500_DEBUG" in:

   include/linux/mfd/abx500/ab8500.h:502

...cannot be valid. It is recommended to delete redundant code.

Suggested-by: Yanjie Ren <renyanjie01@gmail.com>
Signed-off-by: Ying Sun <sunying@nj.iscas.ac.cn>
Link: https://lore.kernel.org/r/20230913084559.18141-1-sunying@nj.iscas.ac.cn


Signed-off-by: Lee Jones <lee@kernel.org>