rum(4): add support for hardware encryption (WEP, TKIP and CCMP).

rum(4): add support for hardware encryption (WEP, TKIP and CCMP).

This diff includes:

* Transmitter Addresses, Keys and TKIP MIC addition to the Security Key Table.
* Proper SEC Control Registers initialization and maintenance.
* Additional flags and values in TX descriptor, which are required for encryption support.
* Error checking in RX path.

Tested:

* Tested on WUSB54GC, STA (WEP, TKIP, CCMP), HOSTAP (CCMP) and IBSS (CCMP, WPA-None) modes.
* rum0: MAC/BBP RT2573 (rev 0x2573a), RF RT2528, STA mode (CCMP+TKIP)

Submitted by:	<s3erios@gmail.com>
Differential Revision:	https://reviews.freebsd.org/D3640