Revert "gpio-mailbox: add support for gflt300"

This reverts commit 6a1811b90df9882cbe798d76461887d0a09a485e.

Change-Id: Ifca0f9c973af1fdf73d37ba0fd0ab5f7924ba81c
diff --git a/gpio-mailbox/Makefile b/gpio-mailbox/Makefile
index 1dc26a4..eaaee20 100644
--- a/gpio-mailbox/Makefile
+++ b/gpio-mailbox/Makefile
@@ -29,8 +29,6 @@
   CFLAGS += -DGFIBER_LT
 else ifeq ($(BR2_TARGET_GENERIC_PLATFORM_NAME),gflt200)
   CFLAGS += -DGFIBER_LT
-else ifeq ($(BR2_TARGET_GENERIC_PLATFORM_NAME),gflt300)
-  CFLAGS += -DGFIBER_LT
 else ifeq ($(BR2_TARGET_GENERIC_PLATFORM_NAME),gfmn100)
   CFLAGS += -DWINDCHARGER
 else ifeq ($(BR2_TARGET_GENERIC_PLATFORM_NAME),gfch100)