armv8: Makefile: build cache files when needed

If no need cache support, not build the cache files, such as in SPL.
Signed-off-by: NPeng Fan <peng.fan@nxp.com>

arch/arm/cpu/armv8/Makefile

@@ -9,14 +9,16 @@ obj-y	+= cpu.o
 ifndef CONFIG_$(SPL_TPL_)TIMER
 obj-$(CONFIG_SYS_ARCH_TIMER) += generic_timer.o
 endif
+ifndef CONFIG_$(SPL_)SYS_DCACHE_OFF
 obj-y	+= cache_v8.o
+obj-y	+= cache.o
+endif
 ifdef CONFIG_SPL_BUILD
 obj-$(CONFIG_ARMV8_SPL_EXCEPTION_VECTORS) += exceptions.o
 else
 obj-y	+= exceptions.o
 obj-y	+= exception_level.o
 endif
-obj-y	+= cache.o
 obj-y	+= tlb.o
 obj-y	+= transition.o
 ifndef CONFIG_ARMV8_PSCI