install_prerequisites: include additional packages to install

"libssl-dev" and "libelf-dev" were found to be required to build linux
kernel on AArch64 host machines. So include them in the list of packages
to be installed as prerequisites. In addition to this, add ""
as well to the list as it required for build of tf-m.

Signed-off-by: Thomas Abraham <thomas.abraham@arm.com>
Signed-off-by: Vivek Gautam <vivek.gautam@arm.com>
Change-Id: Id0a1a00968b9180c6f46fa4441fb2dafc8e6a14b