staging: wilc1000: remove unused code prior to throughput enhancement in SPI

The firmware now uses throughput enhancement code by default for SPI so
remove the previous implementation as its not used anymore. Removed the
use of 'has_thrpt_enh' element as its always true.

Signed-off-by: Ajay Singh <ajay.kathat@microchip.com>
Link: https://lore.kernel.org/r/20200117160157.8706-5-ajay.kathat@microchip.com


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