Group all kernel conditionals for various ioengines in one if block. Change-Id: I14f736c1ab8fce13effeb9ec06731b3d14859941 Signed-off-by: Karol Latecki <karol.latecki@intel.com> Reviewed-on: https://review.gerrithub.io/c/spdk/spdk/+/479818 Tested-by: SPDK CI Jenkins <sys_sgci@intel.com> Community-CI: SPDK CI Jenkins <sys_sgci@intel.com> Reviewed-by: Jim Harris <james.r.harris@intel.com> Reviewed-by: Tomasz Zawadzki <tomasz.zawadzki@intel.com>