powerpc/32: Curb objtool unannotated intra-function call warning

objtool throws the following warning:
arch/powerpc/kexec/relocate_32.o: warning: objtool: .text+0x2bc: unannotated intra-function call

Fix this warning by annotating intra-function call, using
ANNOTATE_INTRA_FUNCTION_CALL macro, to indicate that the branch target
is valid.

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://msgid.link/20221215115258.80810-1-sv@linux.ibm.com