ucm2: sof-soundwire: Correct include file path for dsp.conf

ucm2: sof-soundwire: Correct include file path for dsp.conf

The file path must be given as absolut and not relative, otherwise the
dsp.conf file will not be found:
$ alsaucm dump text
ALSA lib utils.c:364:(uc_mgr_config_load_into) could not open configuration file /usr/share/alsa/ucm2/conf.d/sof-soundwire/../Intel/sof-hda-dsp/dsp.conf
ALSA lib parser.c:78:(uc_mgr_config_load_file) error: failed to open file /usr/share/alsa/ucm2/conf.d/sof-soundwire/../Intel/sof-hda-dsp/dsp.conf: -2
ALSA lib main.c:1554:(snd_use_case_mgr_open) error: failed to import hw:0 use case configuration -2
alsaucm: error failed to open sound card hw:0: No such file or directory

Closes: https://github.com/alsa-project/alsa-ucm-conf/pull/542
Fixes: c9d1f7eafa6c ("UCM2: sof-soundwire: Enable DRC and equalizers for")
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@linux.intel.com>
Signed-off-by: Jaroslav Kysela <perex@perex.cz>