Fix common misspellings

Fixes generated by 'codespell' and manually reviewed.

Signed-off-by: Lucas De Marchi <lucas.demarchi@profusion.mobi>
diff --git a/drivers/dma/at_hdmac.c b/drivers/dma/at_hdmac.c
index 3d7d705..235f53b 100644
--- a/drivers/dma/at_hdmac.c
+++ b/drivers/dma/at_hdmac.c
@@ -167,7 +167,7 @@
 /**
  * atc_assign_cookie - compute and assign new cookie
  * @atchan: channel we work on
- * @desc: descriptor to asign cookie for
+ * @desc: descriptor to assign cookie for
  *
  * Called with atchan->lock held and bh disabled
  */