async_tx: provide __async_inline for HAS_DMA=n archs

To allow an async_tx routine to be compiled away on HAS_DMA=n arch it
needs to be declared __always_inline otherwise the compiler may emit
code and cause a link error.
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

crypto/async_tx/async_xor.c

@@ -30,11 +30,8 @@
 #include <linux/raid/xor.h>
 #include <linux/async_tx.h>
 
-/* do_async_xor - dma map the pages and perform the xor with an engine.
- * 	This routine is marked __always_inline so it can be compiled away
- * 	when CONFIG_DMA_ENGINE=n
- */
-static __always_inline struct dma_async_tx_descriptor *
+/* do_async_xor - dma map the pages and perform the xor with an engine */
+static __async_inline struct dma_async_tx_descriptor *
 do_async_xor(struct dma_chan *chan, struct page *dest, struct page **src_list,
 	     unsigned int offset, int src_cnt, size_t len,
 	     enum async_tx_flags flags,

include/linux/async_tx.h

@@ -21,6 +21,15 @@
 #include <linux/spinlock.h>
 #include <linux/interrupt.h>
 
+/* on architectures without dma-mapping capabilities we need to ensure
+ * that the asynchronous path compiles away
+ */
+#ifdef CONFIG_HAS_DMA
+#define __async_inline
+#else
+#define __async_inline __always_inline
+#endif
+
 /**
  * dma_chan_ref - object used to manage dma channels received from the
  *   dmaengine core.