packagegroup-petalinux:remove deprecated openamp demo packages
packagegroup-petalinux:remove deprecated openamp demo packages

the libmetal-amp-demo has changed to libmetal-demos,
openamp-echo-test, openamp-mat-mul and openamp-proxy-app has been
changed to open-amp-demos.

Signed-off-by: Wendy Liang <cac46fad14f88489ab4dbc3c1082c7dafae20187@xilinx.com>
Signed-off-by: Manjukumar Matha <4c64a17569570cb9f1048973bce031c402b55312@xilinx.com>

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