SPI flash BP3-0 bits are not set

[osresearch]

Once the bootblock is more stabilized, the BP3-0 bits should be set to avoid overwriting it and prevent the root of trust from being subverted by a software attack on the flash chip.

[zaolin]

Works only for the FDT, GBE and BIOS region. For this we need to modify the spi driver for status register support. I have some patches for flashrom itself which can be refactored.

[zaolin]

As always for flashrom patches published, nothing gets merged
https://blogs.coreboot.org/blog/author/hatim/
https://www.flashrom.org/pipermail/flashrom/2016-July/014717.html
https://www.flashrom.org/pipermail/flashrom/2016-July/014737.html

https://github.com/hatimak/flashrom/tree/dev