generic: 5.15: Make support for BoHong bh25q128as generic

generic: 5.15: Make support for BoHong bh25q128as generic

Move the patch for BoHong bh25q128as out of ramips to make it
generic. Not including 6.1.y since the mtd subsystem has changed,
and does not need these changes.

Patch was dropped with ramips updating to 6.1, hence we reintroudce it
here for 5.15 generic.

5.15.y functionality was verified on a Wavlink WL-WN586X3 Rev.a.

Signed-off-by: R Maru <deviantmaru@gmail.com>
[ rebase and add extra info in commit description ]
Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>