Update readme.rst file for v2.1 release

 - Bump version from 2.0 to 2.1.
 - Upgrade recommended FVP version.

Change-Id: I8c7bae8b8285ec6228a2e1ed1bfbe1d8ffc51587
Signed-off-by: Sandrine Bailleux <sandrine.bailleux@arm.com>
1 file changed