rt2x00: Antenna diversity does not work in 2.6.35

The test if antenna diversity is at all enabled uses a local variable
'flags' to prepare the test condition, but uses 'ant->flags' when the test
is evaluated. The effect is that the diversity evaluation will never start.
I can see two solutions, use the 'flag' in the test condition or revert the
local flag change. My attached patch took alternative two.

Then the evaluation start but it will still not switch antenna. The problem
is a code section in rt2x00lib_config_antenna (). The effect of that code
section is that any change the diversity function perform will be
effectively shorten and no antenna selection command issued. The attached
patch will filter out any ANTENNA_SW_DIVERSITY setting but forward all
other

Signed-off-by: Lars Ericsson <lars_ericsson@telia.com>
Signed-off-by: Ivo van Doorn <IvDoorn@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>