LinuxKPI: dmi.h do not rely on implicit includes

Add sys/types.h to dmi.h and do not rely on other files to include
all needed headers in Linux land.  I ran into compile problems with
rtw88 otherwise.

MFC after:	3 days

sys/compat/linuxkpi/common/include/linux/dmi.h

@@ -31,6 +31,7 @@
 #ifndef __LINUX_DMI_H__
 #define	__LINUX_DMI_H__
 
+#include <sys/types.h>
 #include <linux/mod_devicetable.h>
 
 int linux_dmi_check_system(const struct dmi_system_id *);