Documentation: Fix spelling errors

These issues were found and fixed by codespell, a useful tool for
finding spelling errors.

Signed-off-by: Martin Roth <martin@coreboot.org>
Change-Id: If2a8e97911420c19e9365d5c28810b998f2c2ac8
Reviewed-on: https://review.coreboot.org/c/coreboot/+/58078
Reviewed-by: Felix Held <felix-coreboot@felixheld.de>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

Documentation/getting_started/writing_documentation.md

@@ -6,7 +6,7 @@
 That said please always try to write documentation! One problem in the
 firmware development is the missing documentation. In this document
 you will get a brief introduction how to write, submit and publish
-documenation to coreboot.
+documentation to coreboot.
 
 ## Preparations