iwm(4) at boot without corresponding firmware ends in panic (-CURRENT)

[Kyle Evans]

Relevant loader.conf: https://gist.github.com/kevans91/230229d444c15995a00f
Relevant dmesg output: https://gist.github.com/kevans91/c85de8ebd410b3907529

It's not an ideal setup, but the resulting errors and panic seem
incredibly misleading -- the real problem here seems to be failing to
load, in my case, iwm7260fw. Adding `iwm7260fw_load="YES"` to
loader.conf fixes this to work as expected.

Running -CURRENT @ r295683

Thanks,

Kyle Evans