[sw] Fix a few non-absolute includes

Signed-off-by: Miguel Young de la Sota <mcyoung@google.com>
diff --git a/sw/device/lib/hw_sha256.c b/sw/device/lib/hw_sha256.c
index af67cae..0413857 100644
--- a/sw/device/lib/hw_sha256.c
+++ b/sw/device/lib/hw_sha256.c
@@ -4,7 +4,7 @@
 
 #include "sw/device/lib/hw_sha256.h"
 
-#include "hmac.h"
+#include "sw/device/lib/hmac.h"
 
 static const HASH_VTAB HW_SHA256_VTAB = {.init = &hw_SHA256_init,
                                          .update = &hw_SHA256_update,