staging: r8188eu: replace local OFDM_index with single variable

Replace the local OFDM_index array in the
odm_TXPowerTrackingCallback_ThermalMeter_8188E function
with a single variable. Only its first component is used.

Signed-off-by: Martin Kaiser <martin@kaiser.cx>
Link: https://lore.kernel.org/r/20220206161809.423031-4-martin@kaiser.cx


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