busybox: Switch append type to take changes from the user
busybox: Switch append type to take changes from the user

Previously the busybox append from petalinux was using _append to SRC_URI
which worked fine, but if a user wanted to make modification to busyboxs
config, the appends were added after that and were overriding what the
user configured, switch to use += so the user configuration does not
get overriden

Signed-off-by: Alejandro Enedino Hernandez Samaniego <4808ec59fcf4a28be6636a23df6180bf66dbebe1@xilinx.com>

Xilinx/meta-petalinux,Xilinx/meta-petalinux,Xilinx/meta-petalinux,Xilinx/meta-petalinux,Xilinx/meta-petalinux,Xilinx/meta-petalinux