sandbox: Don't use PCI in SPL

PCI is not supported in SPL for sandbox, so avoid using it.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/sandbox/cpu/cpu.c b/arch/sandbox/cpu/cpu.c
index 4975eb2..2def722 100644
--- a/arch/sandbox/cpu/cpu.c
+++ b/arch/sandbox/cpu/cpu.c
@@ -57,7 +57,7 @@
 
 void *map_physmem(phys_addr_t paddr, unsigned long len, unsigned long flags)
 {
-#ifdef CONFIG_PCI
+#if defined(CONFIG_PCI) && !defined(CONFIG_SPL_BUILD)
 	unsigned long plen = len;
 	void *ptr;