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

include/linux/mfd/abx500/ab8500.h

@@ -499,13 +499,7 @@ static inline int is_ab9540_2p0_or_earlier(struct ab8500 *ab)
 
 void ab8500_override_turn_on_stat(u8 mask, u8 set);
 
-#ifdef CONFIG_AB8500_DEBUG
-extern int prcmu_abb_read(u8 slave, u8 reg, u8 *value, u8 size);
-void ab8500_dump_all_banks(struct device *dev);
-void ab8500_debug_register_interrupt(int line);
-#else
 static inline void ab8500_dump_all_banks(struct device *dev) {}
 static inline void ab8500_debug_register_interrupt(int line) {}
-#endif
 
 #endif /* MFD_AB8500_H */