MAINTAINERS: Update PPC status and maintainer

Richard agreed to make odd fixes to PPC tcg parts[1]. This patch makes
the change.

[1] https://lists.gnu.org/archive/html/qemu-ppc/2016-03/msg00657.html

Signed-off-by: Pranith Kumar <bobby.prani@gmail.com>
Signed-off-by: Richard Henderson <rth@twiddle.net>
diff --git a/MAINTAINERS b/MAINTAINERS
index 3fecf45..653f52e 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -1504,8 +1504,8 @@
 F: disas/mips.c
 
 PPC
-M: Vassili Karpov (malc) <av1474@comtv.ru>
-S: Maintained
+M: Richard Henderson <rth@twiddle.net>
+S: Odd Fixes
 F: tcg/ppc/
 F: disas/ppc.c