MAINTAINERS: Fix Sun4v file

Suggested-by: NThomas Huth <thuth@redhat.com>
Reviewed-by: NThomas Huth <thuth@redhat.com>
Signed-off-by: NFam Zheng <famz@redhat.com>
Acked-By: NArtyom Tarasenko <atar4qemu@gmail.com>
Signed-off-by: NMichael Tokarev <mjt@tls.msk.ru>

MAINTAINERS

@@ -778,7 +778,7 @@ F: pc-bios/openbios-sparc64
 Sun4v
 M: Artyom Tarasenko <atar4qemu@gmail.com>
 S: Maintained
-F: hw/sparc64/sun4v.c
+F: hw/sparc64/niagara.c
 F: hw/timer/sun4v-rtc.c
 F: include/hw/timer/sun4v-rtc.h