mmc: meson-gx: replace WARN_ONCE with dev_warn_once about scatterlist size alignment in block mode

Since commit e085b51c74cc ("mmc: meson-gx: check for scatterlist size alignment in block mode"),
support for SDIO SD_IO_RW_EXTENDED transferts are properly filtered but some driver
like brcmfmac still gives a block sg buffer size not aligned with SDIO block,
triggerring a WARN_ONCE() with scary stacktrace even if the transfer works fine
but with possible degraded performances.

Simply replace with dev_warn_once() to inform user this should be fixed to avoid
degraded performance.

This should be ultimately fixed in brcmfmac, but since it's only a performance issue
the warning should be removed.

Fixes: e085b51c74cc ("mmc: meson-gx: check for scatterlist size alignment in block mode")
Reported-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Link: https://lore.kernel.org/r/20210416094347.2015896-1-narmstrong@baylibre.com
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
diff --git a/drivers/mmc/host/meson-gx-mmc.c b/drivers/mmc/host/meson-gx-mmc.c
index eb6c02b..b8b771b 100644
--- a/drivers/mmc/host/meson-gx-mmc.c
+++ b/drivers/mmc/host/meson-gx-mmc.c
@@ -247,8 +247,9 @@
 		 */
 		for_each_sg(data->sg, sg, data->sg_len, i) {
 			if (sg->length % data->blksz) {
-				WARN_ONCE(1, "unaligned sg len %u blksize %u\n",
-					  sg->length, data->blksz);
+				dev_warn_once(mmc_dev(mmc),
+					      "unaligned sg len %u blksize %u, disabling descriptor DMA for transfer\n",
+					      sg->length, data->blksz);
 				return;
 			}
 		}