iop: genconfig: Install devices from active feeds only

When searching for feeds containing image Makefiles with additional devices, do not search in all feed directories, but only in those feeds that are enabled in the currently used profile(s).

This prevents definitions from feeds used in previous invocations of genconfig that used different feeds from leaking in to the next build.

Signed-off-by: Andreas Gnau andreas.gnau@iopsys.eu