Move inc/hf/spci.h to inc/hf/spci_internal.h.

This change disambiguates the include scenarios from the Hf and linux
driver compilations where hf/spci.h would refer to different files.

Change-Id: Ic09ec61c546cca55e8efbea5057ac3cdb321b2a2
diff --git a/src/api.c b/src/api.c
index 90dac19..5506a04 100644
--- a/src/api.c
+++ b/src/api.c
@@ -22,7 +22,7 @@
 #include "hf/check.h"
 #include "hf/dlog.h"
 #include "hf/mm.h"
-#include "hf/spci.h"
+#include "hf/spci_internal.h"
 #include "hf/spinlock.h"
 #include "hf/static_assert.h"
 #include "hf/std.h"