board/ti: Update MAINTAINERS entries with more boards

A few config files have been added without updating MAINTAINERS.

Reported-by: Albert ARIBAUD <albert.u.boot@aribaud.net>
Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/board/ti/am335x/MAINTAINERS b/board/ti/am335x/MAINTAINERS
index c99e06d..7dc2b83 100644
--- a/board/ti/am335x/MAINTAINERS
+++ b/board/ti/am335x/MAINTAINERS
@@ -6,6 +6,7 @@
 F:	configs/am335x_boneblack_defconfig
 F:	configs/am335x_boneblack_vboot_defconfig
 F:	configs/am335x_evm_defconfig
+F:	configs/am335x_gp_evm_defconfig
 F:	configs/am335x_evm_nor_defconfig
 F:	configs/am335x_evm_norboot_defconfig
 F:	configs/am335x_evm_spiboot_defconfig