man: update source path for fdi file and shorten description.
man: update source path for fdi file and shorten description.

Don't describe what the example config file does in the man page, let the
file speak for itself. Point out that fdi files are for servers 1.5 - 1.7
only.

Signed-off-by: Peter Hutterer <b9c50af7afa7642f6f854434cda9ffe54ece8b85@who-t.net>

mad-s/xf86-input-synaptics-absolute,mad-s/xf86-input-synaptics-absolute