mediatek: improve reliability of Fidelix/Dosilicon SPI-NAND

mediatek: improve reliability of Fidelix/Dosilicon SPI-NAND

Prior to performing a PROGRAM LOAD RANDOM DATA operation, a WRITE
ENABLE (06h) command must be issued to change the contents of the
memory array. Following a WRITE ENABLE (06) command, **first a PROGRAM
LOAD (02h or 32h) command must be issued to reset the cache**, then
issue a PROGRAM LOAD RANDOM DATA (84h or 34h) command

This is dirty fix provided to use by MediaTek engineer Sky Huang which
may resolve the "OpenWrt Kiss of Death" issue we've been seeing on the
Linksys E8450 aka. Belkin RT3200. However, it means that everything has
to be re-written with that patch already applied, ie. we need to rebuild
the installer once it is part of snapshot builds to have any effect.

Users already on FIP-in-UBI layout are advised to re-write 'fip' UBI
volume and 'bl2' MTD partition manually once from within Linux after
this fix has been applied.

A similar fix will also be required for U-Boot.

Signed-off-by: Daniel Golle <daniel@makrotopia.org>