Revision A was 0x1000 and B was 0x2000, so I assumed the next would
be revision C valued 0x3000. Alas, it's revision Z with 0x2001...

Change the code accordingly and add detection for the new 800Mhz
profiles.

Code taken from U-Boot commit
cf0818b477 ("stm32mp1: support of STM32MP15x Rev.Z") and
Patch[1] "stm32mp1: add 800 MHz profile support".

[1]: https://st-md-mailman.stormreply.com/pipermail/uboot-stm32/2020-February/002170.html

Signed-off-by: Ahmad Fatoum <ahmad@a3f.at>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>