Add SI_SUB_TASKQ after SI_SUB_INTR and move taskqueue initialization there for EARLY_AP_STARTUP

[jhb]

Looks good to me assuming it boots. A few other places that are using SI_SUB_INIT_IF that might be candidates for now using SI_SUB_TASKQ:

compat/linuxkpi/common/src/linux_work.c:SYSINIT(linux_work_init, SI_SUB_INIT_IF, SI_ORDER_THIRD, linux_work_init, NULL);
compat/linuxkpi/common/src/linux_work.c:SYSUNINIT(linux_work_uninit, SI_SUB_INIT_IF, SI_ORDER_THIRD, linux_work_uninit, NULL);
compat/linuxkpi/common/src/linux_tasklet.c:SYSINIT(linux_tasklet, SI_SUB_INIT_IF, SI_ORDER_THIRD, tasklet_subsystem_init, NULL);
compat/linuxkpi/common/src/linux_tasklet.c:SYSUNINIT(linux_tasklet, SI_SUB_INIT_IF, SI_ORDER_THIRD, tasklet_subsystem_uninit, NULL);
sys/gtaskqueue.h:SYSINIT(taskqgroup_##name, SI_SUB_INIT_IF, SI_ORDER_FIRST,    \
sys/gtaskqueue.h:SYSINIT(taskqgroup_##name, SI_SUB_INIT_IF, SI_ORDER_FIRST,    \

I think gtaskqueue.h is trickier. I bet that this would make it simpler though as it could always do the non-EARLY_AP_STARTUP case and remove the #ifdef's as SI_SUB_TASKQ will always be before SI_SUB_SMP.