There isn't an efficiency centrality implemented in MATLAB. Based on the paper I quickly read, it seems you would best compute this using
P = sum(D, 'all') / n / (n-1);
Pi = sum(D, 'all') / (n-1) / (n-2);
Please verify this matches the definition of efficiency centrality you're looking for, since there seem to be modified versions described.
There might be more efficient implementations than this, but I didn't find any paper mentioning a specific algorithm to be used - and this matches the definitions in the paper.