DEVELOPERS: add maintainer for pc_x86_64_* defconfigs

I've been using this packages to test changes in the grub package, so
I can maintain them.

Signed-off-by: Erico Nunes <nunes.erico@gmail.com>
Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

DEVELOPERS

@@ -535,6 +535,7 @@ F:	package/efivar/
 F:	package/fwts/
 F:	package/spi-tools/
 F:	package/xdotool/
+F:	configs/pc_x86_64_*
 
 N:	Erik Stromdahl <erik.stromdahl@gmail.com>
 F:	package/mxsldr/