wifi: wilc1000: remove use of has_thrpt_enh3 flag

The 'enhance throughput flow' algorithm is used by default. So older
sections of the code are removed so as to always use this new algorithm.

Signed-off-by: Prasurjya Rohan Saikia <prasurjya.rohansaikia@microchip.com>
Acked-by: Ajay Kathat <ajay.kathat@microchip.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20230710094401.235222-1-prasurjya.rohansaikia@microchip.com