sandbox: Add a dummy dcache_status() function

This adds dcache_status() so that code using it can build
without error on sandbox. This is required in preparation
of adding cache handling into get_ram_size function.

Signed-off-by: Emanuele Ghidoli <emanuele.ghidoli@toradex.com>
Signed-off-by: Francesco Dolcini <francesco.dolcini@toradex.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

arch/sandbox/cpu/cpu.c

@@ -286,6 +286,11 @@ void sandbox_set_enable_pci_map(int enable)
 	enable_pci_map = enable;
 }
 
+int dcache_status(void)
+{
+	return 1;
+}
+
 void flush_dcache_range(unsigned long start, unsigned long stop)
 {
 }