[xu3][gst-omx] Fix path substitution in gstomx.conf

[xu3][gst-omx] Fix path substitution in gstomx.conf

Replace / with | in the sed command, as it is done for other targets,
so @LIBDIR@ gets replaced with a proper file path in gstomx.conf.

Now the substitution doesn't work as sed gets confused by slashes
in %{_libdir} variable. %{_libdir} may be /usr/lib and then the
command evaluates to "sed -i -e 's/@LIBDIR@//usr/lib/g'", which
doesn't work as expected.

The sed error is being reported during package installation:

sed: -e expression #1, char 13: unknown option to `s'

This patch fixes initialization of gst-omx plugin on Odroid XU3
indicated by GStreamer error logs:

W/GST_LOG : ERROR  omx gstomx.c:3006:plugin_init: Core '@LIBDIR@/libExynosOMX_Core.so' does not exist for element 'omxdec_mpeg2'
W/GST_LOG : ERROR  omx gstomx.c:3006:plugin_init: Core '@LIBDIR@/libExynosOMX_Core.so' does not exist for element 'omxdec_mpeg4'
W/GST_LOG : ERROR  omx gstomx.c:3006:plugin_init: Core '@LIBDIR@/libExynosOMX_Core.so' does not exist for element 'omxdec_h263'
W/GST_LOG : ERROR  omx gstomx.c:3006:plugin_init: Core '@LIBDIR@/libExynosOMX_Core.so' does not exist for element 'omxdec_h264'
W/GST_LOG : ERROR  omx gstomx.c:3006:plugin_init: Core '@LIBDIR@/libExynosOMX_Core.so' does not exist for element 'omxenc_h264'
W/GST_LOG : ERROR  omx gstomx.c:3006:plugin_init: Core '@LIBDIR@/libExynosOMX_Core.so' does not exist for element 'omxenc_mpeg4'
W/GST_LOG : ERROR  omx gstomx.c:3006:plugin_init: Core '@LIBDIR@/libExynosOMX_Core.so' does not exist for element 'omxenc_h263'
W/GST_LOG : WARN   GST_PLUGIN_LOADING gstplugin.c:527:gst_plugin_register_func: plugin "/usr/lib/gstreamer-1.0/libgstomx.so" failed to initialise

Change-Id: Ia21269e9d67742e49d390b6beaa4c0c06c969057
Suggested-by: Lukasz Stelmach <l.stelmach@samsung.com>
Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>