wic: Hook up BootimgEFIPlugin and BootimgPcbiosPlugin plugins
Remove all the Wic_PartData and DirectImageCreator code now
implemented by the BootimgEFIPlugin and BootimgPcbiosPlugin plugins,
as well as all the special-cased boot_type code, significantly
cleaning up the code.
Replace the calling code with general-purpose plugin invocations, in
essence calling the appropriate implementations at run-time based on
the --source value in effect.
Change the directdisk.wks and mkefidisk.wks scripts to make use of the
new plugins.
Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
