powerpc/pseries: Remove unused cede related functions

Remove extended_cede_processor() and its helpers as
extended_cede_processor() has no callers since
commit 48f6e7f6("powerpc/pseries: remove cede offline state for CPUs")

Signed-off-by: Gautam Menghani <gautam@linux.ibm.com>
Acked-by: Naveen N Rao <naveen@kernel.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20240514132457.292865-1-gautam@linux.ibm.com