bcm53xx: add ramdisk to FEATURES

Cisco/Meraki mx64/mx65 targets require initramfs
( ramdisk) for install.
Add it to default target build.

Signed-off-by: Evan Jobling <evan.jobling at mslsc.com.au>
Signed-off-by: Rosen Penev <rosenp@gmail.com>
Link: openwrt/openwrt#22835
Signed-off-by: Robert Marko <robimarko@gmail.com>

Author: neheb

target/linux/bcm53xx/Makefile

@@ -7,7 +7,7 @@ include $(TOPDIR)/rules.mk
 ARCH:=arm
 BOARD:=bcm53xx
 BOARDNAME:=Broadcom BCM47xx/53xx (ARM)
-FEATURES:=squashfs nand usb pci pcie gpio pwm
+FEATURES:=squashfs nand usb pci pcie gpio pwm ramdisk
 CPU_TYPE:=cortex-a9
 SUBTARGETS:=generic