gemini: try fis-index-block with 128 KiB sectors

gemini: try fis-index-block with 128 KiB sectors

Steven Maddox reported in the OpenWrt bugzilla, that his
RaidSonic IB-NAS4220-B was no longer booting with the new
OpenWrt 21.02 (uses linux 5.10's device-tree). However, it was
working with the previous OpenWrt 19.07 series (uses 4.14).

(This is still under investigation.)

Bugzilla: https://bugs.openwrt.org/index.php?do=details&task_id=4137
Reported-by: Steven Maddox <s.maddox@lantizia.me.uk>
Signed-off-by: Christian Lamparter <chunkeey@gmail.com>