rt2800: calculate tx power temperature compensation on selected chips

Currently implemented temperature compensation is only valid on some of
supported chips. Other chips do not need temperature compensation or
need different way to do this (not yet implemented in the rt2800
driver). Trying to do run rt2800_get_gain_calibration_delta() when this
is not appropriate on particular chip gives bogus result of TX power
and can make connection unstable.

This is follow up to commit 8c8d2017
"rt2800: fix RT5390 & RT3290 TX power settings regression". On that
commit we avoid setting BBP_R1 register, but the real problem is wrong
temperature compensation calculation.

Reported-and-tested-by: Ronald Wahl <ronald.wahl@raritan.com>
Debugged-by: Ronald Wahl <ronald.wahl@raritan.com>
Cc: Mike Romberg <mike-romberg@comcast.net>
Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>