MAINTAINERS: GDB: Update e-mail address

This entry was created with my personal e-mail address. Update this
entry to my open-source kernel.org account.

Signed-off-by: Kieran Bingham <kbingham@kernel.org>
diff --git a/MAINTAINERS b/MAINTAINERS
index 174c0c3d..c25060e 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -5931,7 +5931,7 @@
 
 GDB KERNEL DEBUGGING HELPER SCRIPTS
 M:	Jan Kiszka <jan.kiszka@siemens.com>
-M:	Kieran Bingham <kieran@bingham.xyz>
+M:	Kieran Bingham <kbingham@kernel.org>
 S:	Supported
 F:	scripts/gdb/