MAINTAINERS: Add myself as reviewer for PowerPC TCG CPUs

I have been working on Power ISA for a long time now and have mostly
contributed in TCG instruction translation area (moved 300+ instructions to
decodetree as of yet) and would like to continue contributing to PPC TCG in
best possible ways I can. I think it's time to step up and assist in reviewing
related patches to enable myself contribute more effectively in this direction.

Signed-off-by: Chinmay Rath <rathc@linux.ibm.com>
Reviewed-by: Cédric Le Goater <clg@redhat.com>
Signed-off-by: Harsh Prateek Bora <harshpb@linux.ibm.com>
Link: https://lore.kernel.org/qemu-devel/20250724100623.3071131-4-harshpb@linux.ibm.com
Signed-off-by: Cédric Le Goater <clg@redhat.com>

MAINTAINERS

@@ -296,6 +296,7 @@ F: tests/tcg/openrisc/
 PowerPC TCG CPUs
 M: Nicholas Piggin <npiggin@gmail.com>
 M: Daniel Henrique Barboza <danielhb413@gmail.com>
+R: Chinmay Rath <rathc@linux.ibm.com>
 L: qemu-ppc@nongnu.org
 S: Odd Fixes
 F: target/ppc/