orinoco: Make firmware download logic more generic

Ensure PDA read is terminated.
Prevent invalid programming blocks from causing reads outside the
firmware image
Turn off aux stuff when finished.
Option to program in limited block sizes (controlled by macro).
Option to read PDA from EEPROM.

Signed-off-by: David Kilroy <kilroyd@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>