Correct the nand ecc initialization code
This fixes the issue of incorrect nand ecc
init if no device is found in ecc_matrix then
it endsup ecc init with junk initialization
instead of the most suited one.

Signed-off-by: Siva Durga Prasad Paladugu <sivadur@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>