Platform-only build of gftv100 doesn't use BCM_NEXUS.

We need a different way to detect which gpio-mailbox pinout to use.  Let's
do what we ended up doing with the other platforms, and just hardcode it by
model number.  b/33070819

Change-Id: If1dc712149081355a1cd7add9342e26d94a3985e
diff --git a/gpio-mailbox/Makefile b/gpio-mailbox/Makefile
index f6cb77f..bd29573 100644
--- a/gpio-mailbox/Makefile
+++ b/gpio-mailbox/Makefile
@@ -21,10 +21,14 @@
 LDFLAGS += $(EXTRA_LDFLAGS)
 
 # enable the platform we're supporting
-ifeq ($(BR2_PACKAGE_BCM_NEXUS),y)
-  CFLAGS += -DBROADCOM
-else ifeq ($(BR2_PACKAGE_MINDSPEED_DRIVERS),y)
+ifeq ($(BR2_PACKAGE_MINDSPEED_DRIVERS),y)
   CFLAGS += -DMINDSPEED
+else ifeq ($(BR2_TARGET_GENERIC_PLATFORM_NAME),gfibertv)
+  CFLAGS += -DBROADCOM
+else ifeq ($(BR2_TARGET_GENERIC_PLATFORM_NAME),gftv200)
+  CFLAGS += -DBROADCOM
+else ifeq ($(BR2_TARGET_GENERIC_PLATFORM_NAME),gftv254)
+  CFLAGS += -DBROADCOM
 else ifeq ($(BR2_TARGET_GENERIC_PLATFORM_NAME),gflt110)
   CFLAGS += -DGFIBER_LT
 else ifeq ($(BR2_TARGET_GENERIC_PLATFORM_NAME),gflt200)