sched/core: Simplify code by removing duplicate #ifdefs

There's a few cases of nested #ifdefs in the scheduler code
that can be simplified:

  #ifdef DEFINE_A
  ...code block...
    #ifdef DEFINE_A       <-- This is a duplicate.
    ...code block...
    #endif
  #else
    #ifndef DEFINE_A     <-- This is also duplicate.
    ...code block...
    #endif
  #endif

More details about the script and methods used to find these code
patterns can be found at:

  https://lore.kernel.org/all/20240118080326.13137-1-sshegde@linux.ibm.com/



No change in functionality intended.

[ mingo: Clarified the changelog. ]

Signed-off-by: Shrikanth Hegde <sshegde@linux.ibm.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lore.kernel.org/r/20240216061433.535522-1-sshegde@linux.ibm.com