build: Don't compile DPDK when doing make install

Signed-off-by: Ben Walker <benjamin.walker@intel.com>
Change-Id: I146bc479ddb2c84760a21e4f5a009b9ec8e53700
Reviewed-on: https://review.spdk.io/gerrit/c/spdk/spdk/+/2644


Community-CI: Mellanox Build Bot
Community-CI: Broadcom CI
Tested-by: SPDK CI Jenkins <sys_sgci@intel.com>
Reviewed-by: Paul Luse <paul.e.luse@intel.com>
Reviewed-by: Jim Harris <james.r.harris@intel.com>
Reviewed-by: Darek Stojaczyk <dariusz.stojaczyk@intel.com>