ui/crumbs/hobprefs: re-enable reloading of data after prefs changes

ui/crumbs/hobprefs: re-enable reloading of data after prefs changes

When disabling the toolchain w/ headers checkbox in an early commit I
accidentally disabled too much code. This re-enables adding the custom
response handler to the Preferences dialog which triggeres a reparse of
the metadata when appropriate preference changes are made.

Fixes [YOCTO #1479]

(Bitbake rev: bdbd724e806c9ca69cc1508bac7ec0a2dce95543)

Signed-off-by: Joshua Lock <josh@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>