powerpc/85xx: Fix unannotated intra-function call warning

objtool throws the following warning:
  arch/powerpc/kernel/head_85xx.o: warning: objtool: .head.text+0x1a6c:
  unannotated intra-function call

Fix the warning by annotating KernelSPE symbol with SYM_FUNC_START_LOCAL
and SYM_FUNC_END macros.

Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Sathvika Vasireddy <sv@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20230128124138.1066176-1-sv@linux.ibm.com