powerpc: remove unused KCSAN_SANITIZE_early_64.o in Makefile

Commit 2fb857bc ("powerpc/kcsan: Add exclusions from instrumentation")
added KCSAN_SANITIZE_early_64.o to arch/powerpc/kernel/Makefile, while
it does not compile early_64.o.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20240216135817.2003106-1-masahiroy@kernel.org

arch/powerpc/kernel/Makefile

@@ -55,7 +55,6 @@ CFLAGS_btext.o += -DDISABLE_BRANCH_PROFILING
 endif
 
 KCSAN_SANITIZE_early_32.o := n
-KCSAN_SANITIZE_early_64.o := n
 KCSAN_SANITIZE_cputable.o := n
 KCSAN_SANITIZE_btext.o := n
 KCSAN_SANITIZE_paca.o := n