sdimage_class: eliminate 2GB exception for BeagleBone

Gerald has said his supply of 2GB SD cards for BeagleBone has
gone away, so we are back to 4GB cards.  No more need for this
exeption:

Signed-off-by: Jason Kridner <jdk@ti.com>
Signed-off-by: Koen Kooi <koen@dominion.thruhere.net>

classes/sdcard_image.bbclass

@@ -12,9 +12,8 @@ LOOPDEV ?= "/dev/loop1"
 LOOPDEV_BOOT ?= "/dev/loop2"
 LOOPDEV_FS ?= "/dev/loop3"
 
-# Default to 4GiB images, but use 2GiB images for beaglebone
+# Default to 4GiB images
 SDIMG_SIZE ?= "444" 
-SDIMG_SIZE_beaglebone = "222"
 
 BOOTPARTNAME_beaglebone = "BEAGLE_BONE"
 BOOTPARTNAME ?= "${MACHINE}"