docs(maintainers): update measured boot code owners

Propose myself as a code owner of the measured boot module.

Also do a couple of updates along the way:

 - Add the measured boot bindings document to the list of measured
   boot files.

 - Fix the list of FVP files. plat/arm/board/fvp/fvp_measured_boot.c
   does not exist anymore. It has been replaced by
   plat/arm/board/fvp/fvp_measured_{bl1,bl2,common}_boot.c files.

Change-Id: Ifb34f4f7c704b1db966b44428bbffd48c5e3c42b
Signed-off-by: Sandrine Bailleux <sandrine.bailleux@arm.com>