Expand the list of compatible devices this driver works with.  Increase
the target frequency from 1 to 10 MHz because these SoCs are plenty fast
enough to benefit from the extra event timer resolution.
Add manpage for urtwnfw, the Realtek RTL8188CU/RTL8192CU firmware
module.  Also fix a few nits in urtwn.4.

Reviewed by:	rpaulo