Older cards with a Prism 2 Chipset can connect to WPA encrypted networks using wpa_supplicant with a station firmware above 1.8.0!
To check for your firmware look into dmesg
$ dmesg | grep wifi0
There should be some lines similar to these:
[ 2.132238] wifi0: NIC: id=0x801b v1.0.0 [ 2.173409] wifi0: PRI: id=0x15 v1.1.1 [ 2.213987] wifi0: STA: id=0x1f v1.8.0
If your STA firmware is above 1.8.0, you can connect to WPA networks without updating!
Do this at your own risk, it can brick your card! I recommend update only to 1.8.0, not above because there are some bugs in later firmwares.
This can be done with the prism2_srec utility from the package hostap-utils. https://wiki.debian.org/hostap#Firmware
You can find the firmware files here: http://www.sp-net.at/prism/firmware/