image_types_fsl.bbclass: use dd's option fsync instead of sync
The shell command sync flushes all filesystem buffers in the system. On
a bigger multiuser system there are multiple gigs of data sometimes in
the buffer which then are written out to disk at once. It's better to
only flush the specific file with dd's option 'fsync'.
Change-Id: I6476444dbbc28e4f8756066e531734ef1de71fdb Signed-off-by: Stefan Christ <s.christ@phytec.de> Tested-by: Nikolay Dimitrov <picmaster@mail.bg> Signed-off-by: Otavio Salvador <otavio@ossystems.com.br>
