soc: qcom: cmd-db: Fix compilation error when CMD_DB is disabled

If CONFIG_QCOM_COMMAND_DB=n the following compilation errors will be
seen. Fix this by including the appropriate linux headers.

./include/soc/qcom/cmd-db.h: In function ‘cmd_db_read_aux_data’:
./include/soc/qcom/cmd-db.h: error: implicit declaration of function ‘ERR_PTR’;

Reviewed-by: Stephen Boyd <[e-mail]>
Signed-off-by: Sibi Sankar <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Bjorn Andersson <[e-mail]>

include/soc/qcom/cmd-db.h

···
 #ifndef __QCOM_COMMAND_DB_H__
 #define __QCOM_COMMAND_DB_H__
 
+#include <linux/err.h>
 
 enum cmd_db_hw_type {
 	CMD_DB_HW_INVALID = 0,