riscv: skip errata_cip_453.o if CONFIG_ERRATA_SIFIVE_CIP_453 is disabled

The errata_cip_453.o should be built only when the Kconfig
CONFIG_ERRATA_SIFIVE_CIP_453 is enabled.
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Vincent <vincent.chen@sifive.com>
Fixes: 0e0d4992 ("riscv: enable SiFive errata CIP-453 and CIP-1200 Kconfig only if CONFIG_64BIT=y")
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>

arch/riscv/errata/sifive/Makefile

-obj-y += errata_cip_453.o
+obj-$(CONFIG_ERRATA_SIFIVE_CIP_453) += errata_cip_453.o
 obj-y += errata.o