treewide: Fix typos in libata.xml

This patch fix spelling typos found in Documentation/Docbook/libata.xml.
It is because the file was generated from comments in source,
I had to fix comments in libata-core.c

Signed-off-by: Masanari Iida <standby24x7@gmail.com>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Tejun Heo <tj@kernel.org>