During testing of bcm43xx interference mitigation, two problems were
discovered:

(1) When the MANUALWLAN mode was set, routines _stack_save and _stack_restore
    generated assertions that were traced to saving ILT registers with addresses
    > 0xFFF. This problem was fixed by adding one bit to the field used for
    the offset, and subtracting one bit from the space used for the id.
(2) In MANUALWLAN mode, the IRQ XMIT errors are generated. The cause of these
    errors has not yet been located. Any suggestions on debugging this problem
    would be greatly appreciated.
Signed-off-by: NLarry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>