ASoC: q6dsp: q6apm: make g_apm static

This patch fixes the following sprse warning:

sound/soc/qcom/qdsp6/q6apm.c:30:14: sparse: warning: symbol 'g_apm' was not declared. Should it be static?

No functional change intended
Signed-off-by: Min-Hua Chen <minhuadotchen@gmail.com>
Link: https://lore.kernel.org/r/20230713151744.86072-1-minhuadotchen@gmail.comSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/qcom/qdsp6/q6apm.c

@@ -27,7 +27,7 @@ struct apm_graph_mgmt_cmd {
 
 #define APM_GRAPH_MGMT_PSIZE(p, n) ALIGN(struct_size(p, sub_graph_id_list, n), 8)
 
-struct q6apm *g_apm;
+static struct q6apm *g_apm;
 
 int q6apm_send_cmd_sync(struct q6apm *apm, struct gpr_pkt *pkt, uint32_t rsp_opcode)
 {