bcm53xx: image: use one style of adding TARGET_DEVICES entries

It just makes code consistent. This trivial change may be a 17.01
candidate to provide simpler backporting experience.

Signed-off-by: Rafał Miłecki <rafal@milecki.pl>

target/linux/bcm53xx/image/Makefile

@@ -218,6 +218,7 @@ define Device/netgear-r6250
   $(Device/netgear)
   NETGEAR_BOARD_ID := U12H245T00_NETGEAR
 endef
+TARGET_DEVICES += netgear-r6250
 
 define Device/netgear-r6300-v2
   DEVICE_TITLE := Netgear R6300 V2
@@ -225,6 +226,7 @@ define Device/netgear-r6300-v2
   $(Device/netgear)
   NETGEAR_BOARD_ID := U12H240T00_NETGEAR
 endef
+TARGET_DEVICES += netgear-r6300-v2
 
 define Device/netgear-r7000
   DEVICE_TITLE := Netgear R7000
@@ -248,6 +250,7 @@ define Device/netgear-r8000
   $(Device/netgear)
   NETGEAR_BOARD_ID := U12H315T00_NETGEAR
 endef
+TARGET_DEVICES += netgear-r8000
 
 define Device/netgear-r8500
   DEVICE_TITLE := Netgear R8500
@@ -263,6 +266,7 @@ define Device/smartrg-sr400ac
   IMAGES := trx
   IMAGE/trx := append-rootfs | trx-serial
 endef
+TARGET_DEVICES += smartrg-sr400ac
 
 define Device/tenda-ac9
   DEVICE_TITLE := Tenda AC9
@@ -281,8 +285,4 @@ define Device/tplink-archer-c9-v1
 endef
 TARGET_DEVICES += tplink-archer-c9-v1
 
-TARGET_DEVICES += \
-	netgear-r6250 netgear-r6300-v2 netgear-r8000 \
-	smartrg-sr400ac
-
 $(eval $(call BuildImage))