staging: wilc1000: rename tsf_hi element of network_info struct

Rename 'tsf_hi' element in network_info struct as it's not used to store
only the higher 32-bit value but the complete 64-bit tsf value.

Signed-off-by: Ajay Singh <ajay.kathat@microchip.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>