[Meta-mender] Add new partition

Hi,

In my image have 2 rawcopy partition before boot and root, For boot the our image those two are required Can help me to get these in sdimage.

u-boot-spl.bin - mmcblk0p1 No fs
u-boot.itb - mmcblk0p2 No fs
boot - mmcblk0p3 vfat
root - mmcblk0p4 ext4