staging: r8188eu: bTXPowerTracking is set but not used

bTXPowerTracking in struct odm_rf_cal is set but not used.
Remove it.

Signed-off-by: Martin Kaiser <martin@kaiser.cx>
Link: https://lore.kernel.org/r/20220205113741.379070-5-martin@kaiser.cx


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>