MLK-18497-9: ASoC: fsl: dsp: Export xf_client_alloc

While at it add include guard to dsp.h

Reviewed-by: Cosmin-Gabriel Samoila <cosmin.samoila@nxp.com>
Signed-off-by: Shengjiu Wang <shengjiu.wang@nxp.com>
Signed-off-by: Daniel Baluta <daniel.baluta@nxp.com>
(cherry picked from commit a1c7e9a833bec9e517cc17c8e84e330dab198a7b)
Signed-off-by: Vipul Kumar <vipul_kumar@mentor.com>
Signed-off-by: Srikanth Krishnakar <Srikanth_Krishnakar@mentor.com>
Signed-off-by: Vipul Kumar <vipul_kumar@mentor.com>