MLK-20466: mxc-jpeg: Fix coverity issues

Return int from get_sof (-1 for error), the result is later on
compared with -1 literal.

Fix memory leak from print_nbuf_to_eoi, when !mxc_jpeg_tracing.

Signed-off-by: Mirela Rabulea <mirela.rabulea@nxp.com>
Reviewed-by: Robert Chiras <robert.chiras@nxp.com>