projects/ad4630_fmc: update AD4630_FMC documentation

Updated the documentation with the new variables and features
of the AD4630_FMC project. It is describing how to compile with
the NUM_OF_CHANNEL, LANES_PER_CHANNEL, and INTERLEAVE_MODE. It
also describes the EMIO inserted for controlling the CNV output.

Signed-off-by: Carlos Souza <carlos.souza@analog.com>

Author: caosjr