The fmc devices are now children of their own device.

This is what we had with fmc-fakedev and 1 mezzanine using a custom eeprom:
tha lead to custom names):

spusa.root# ls -l /sys/bus/fmc/devices/
 FmcDelay1ns4cha-f001 -> ../../../devices/fmc/FmcDelay1ns4cha-f001/

And this is what we have now:

spusa.root# ls -l /sys/bus/fmc/devices/
 FmcDelay1ns4cha-f001 -> ../../../devices/fake-fmc-carrier/FmcDelay1ns4cha-f001/
Signed-off-by: Alessandro Rubini <rubini@gnudd.com>