m68k: Implement a default flush_dcache_all

Implement a weak default version of flush_dcache_all which is based on
the ARM default, which is to flush the entire range via
flush_dcache_range(...).

Acked-by: Angelo Dureghello <angelo@kernel-space.org>
Acked-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Signed-off-by: Tom Rini <trini@konsulko.com>

arch/m68k/lib/cache.c

@@ -134,6 +134,15 @@ void dcache_invalid(void)
 #endif
 }
 
+/*
+ * Default implementation:
+ * do a range flush for the entire range
+ */
+__weak void flush_dcache_all(void)
+{
+	flush_dcache_range(0, ~0);
+}
+
 __weak void invalidate_dcache_range(unsigned long start, unsigned long stop)
 {
 	/* An empty stub, real implementation should be in platform code */