staging: wilc1000: fix line over 80 characters in spi_cmd_complete()

Refactor spi_cmd_complete() to fix the line over 80 char issues reported
by checkpatch.pl script.

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