MAINTAINERS: add myself as PATA drivers reviewer

Add myself as a reviewer for the libata PATA drivers -- there is
activity in this area still... 8-)
Having been hacking on ATA from the early 90s, I think I deserved this
highly responsible position, at last! :-)

Signed-off-by: Sergey Shtylyov <s.shtylyov@omp.ru>
Signed-off-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>