MAINTAINERS: powerpc: Remove myself as a reviewer

I haven't been able to participate and help with this as much as I had
hoped, and it doesn't look like I will be able to spend time on powerpc
going forward.

Signed-off-by: Naveen N Rao (AMD) <[email protected]>
Signed-off-by: Madhavan Srinivasan <[email protected]>
Link: https://patch.msgid.link/[email protected]

Author: rnav

MAINTAINERS

@@ -13626,7 +13626,6 @@ M:	Madhavan Srinivasan <[email protected]>
 M:	Michael Ellerman <[email protected]>
 R:	Nicholas Piggin <[email protected]>
 R:	Christophe Leroy <[email protected]>
-R:	Naveen N Rao <[email protected]>
 L:	[email protected]
 S:	Supported
 W:	https://github.com/linuxppc/wiki/wiki