wifi: wilc1000: correct CRC7 calculation

Document

    ATWILC1000/ATWILC3000
    Baremetal Wi-Fi/BLE Link Controller Software Design Guide

    https://tinyurl.com/yer2xhyc



says that bit 0 of the CRC7 code must always be a 1.

I confirmed that today with a logic analyzer: setting bit 0 causes
wilc1000 to accept a command with CRC7 enabled, whereas clearing bit 0
causes wilc1000 to reject the command with a CRC error.

Signed-off-by: David Mosberger-Tang <davidm@egauge.net>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://msgid.link/20240207050736.2717641-1-davidm@egauge.net