MFC 240921:
Add optional entropy harvesting for software interrupts in swi_sched()
as controlled by kern.random.sys.harvest.swi.  SWI harvesting feeds into
the interrupt FIFO and each event is estimated as providing a single bit of
entropy.
MFC 241130:
Rename the module for 'device enc' to "if_enc" to avoid conflicting with
the CAM "enc" peripheral (part of ses(4)).  Previously the two modules
used the same name, so only one was included in a linked kernel causing
enc0 to not be created if you added IPSEC to GENERIC.  The new module
name follows the pattern of other network interfaces (e.g. "if_loop").