gw_flash: Add support for Winbond W25Q128JWSIQ 16MB Flash

[unhold]

W25Q128JWSIQ is widely available in SOIC-8.
Some testing done.

[unhold]

It worked flawlessly, I could flash it multiple times without any issue. In fact, it also worked with the default configuration. But the first try after the pull request failed, I have to figure out why.

[kbeckmann]

Thanks. Hope you can find what’s wrong. The pr looks good otherwise and the commands seem to be correct according to the data sheet. Perhaps some init sequence might be needed to reset the chip?

[unhold]

Thank you for checking it!
Finally had the inspiration to figure it out: I had protection bits in the status registers set, because I accidentally executed init_mx_issi() on the Winbond. The pull-requested code was fine.