qemu/: fix some comment spelling errors

I found that there are many spelling errors in the comments of qemu,
so I used the spellcheck tool to check the spelling errors
and finally found some spelling errors in the folder.

Signed-off-by: zhaolichang <zhaolichang@huawei.com>
Reviewed-by: Alex Bennee <alex.bennee@linaro.org>
Message-Id: <20200917075029.313-2-zhaolichang@huawei.com>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>
diff --git a/hmp-commands.hx b/hmp-commands.hx
index 60f395c..27c4bbe 100644
--- a/hmp-commands.hx
+++ b/hmp-commands.hx
@@ -1267,7 +1267,7 @@
     },
 SRST
 ``drive_backup``
-  Start a point-in-time copy of a block device to a specificed target.
+  Start a point-in-time copy of a block device to a specified target.
 ERST
 
     {