OWNERS: Add myself as an owner

There are still some IPMID patches that need to be reviewed by the
community, and some are ready to be merged, so I would like to take
on some of Vernon and Tom's work and help review them.
However, for feature and requirement changes, they still need final
review.

Here are my contributions to phosphor-host-ipmid repository [1]:
[1]: https://github.com/openbmc/phosphor-host-ipmid/commits/master/?author=lxwinspur

Change-Id: I826d9be41186e3251a220b154caaeee5e3047455
Signed-off-by: George Liu <liuxiwei@ieisystem.com>
diff --git a/OWNERS b/OWNERS
index 810291a..9d16375 100644
--- a/OWNERS
+++ b/OWNERS
@@ -32,13 +32,13 @@
 # data within them will be kept sorted.
 
 owners:
+- liuxiwei@ieisystem.com
 - rushtotom@gmail.com
 - vernon.mauery@gmail.com
 
 reviewers:
 - anoo@us.ibm.com
 - deepak.kodihalli.83@gmail.com
-- liuxiwei@ieisystem.com
 - ratankgupta31@gmail.com
 
 matchers: