MAINTAINERS: add F: and acronyms

Add F: definition since it is being used.

Expand acronyms or add them so that users of MAINTAINERS file can find
entries more easily.

Correct driver spelling.

Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>