Hob: a minor fix on pmake

Hob: a minor fix on pmake

params["pmake"] should be in the format "-j int".
When loading/saving "PARALLEL_MAKE" into templates, configuration.pmake will be
converted into "-j int", as "PACKAGE_CLASSES" and "BBLAYERS" do.

For "PACKAGE_CLASSES" and "BBLAYERS", params["pclass"] and params["layer"] are
also strings rather than the types of configuration.curr_package_format and
configuration.layers.

(Bitbake rev: d49db15badb77855cef855ee73430fcbc16b6916)

Signed-off-by: Shane Wang <shane.wang@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>