openpower: Add myself to maintainers

I look after pdbg, aspeed-lpc-ctrl, skiboot (pflash, gard) and
hostboot_settings in this repository.

(From meta-openpower rev: 8358783c014bc2787af6e02792d98cb286ec7b6d)

Change-Id: Icc243c1221ceb7098c2d0fd87fbb94e030b0fe56
Signed-off-by: Joel Stanley <joel@jms.id.au>
Signed-off-by: Brad Bishop <bradleyb@fuzziesquirrel.com>
diff --git a/meta-openpower/MAINTAINERS b/meta-openpower/MAINTAINERS
index bfe81de..d95ebb6 100644
--- a/meta-openpower/MAINTAINERS
+++ b/meta-openpower/MAINTAINERS
@@ -43,3 +43,4 @@
 -------------------------
 
 M:  Brad Bishop <bradleyb@fuzziesquirrel.com> <radsquirrel!>
+M:  Joel Stanley <joel@jms.id.au> <shenki!>