async_tx: add sum check flags

Replace the flat zero_sum_result with a collection of flags to contain
the P (xor) zero-sum result, and the soon to be utilized Q (raid6 reed
solomon syndrome) zero-sum result.  Use the SUM_CHECK_ namespace instead
of DMA_ since these flags will be used on non-dma-zero-sum enabled
platforms.

Reviewed-by: Andre Noll <maan@systemlinux.org>
Acked-by: Maciej Sosnowski <maciej.sosnowski@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

diff --git a/crypto/async_tx/async_xor.c b/crypto/async_tx/async_xor.c
index 1e96c4d..78fb778 100644
--- a/crypto/async_tx/async_xor.c
+++ b/crypto/async_tx/async_xor.c
@@ -246,7 +246,7 @@
  */
 struct dma_async_tx_descriptor *
 async_xor_val(struct page *dest, struct page **src_list, unsigned int offset,
-	      int src_cnt, size_t len, u32 *result,
+	      int src_cnt, size_t len, enum sum_check_flags *result,
 	      struct async_submit_ctl *submit)
 {
 	struct dma_chan *chan = async_tx_find_channel(submit, DMA_XOR_VAL,
@@ -304,7 +304,7 @@
 
 		async_tx_quiesce(&tx);
 
-		*result = page_is_zero(dest, offset, len) ? 0 : 1;
+		*result = !page_is_zero(dest, offset, len) << SUM_CHECK_P;
 
 		async_tx_sync_epilog(submit);
 		submit->flags = flags_orig;