Magnetization Inductance vs. Transformer Inductance
The transformer primary, in the absence of a load on the secondary, is just an inductor and, as with any inductor, the current that passes through it causes magnetization hence, the current that flows into the transformer primary with no secondary load is basically the magnetization current.

It's probably better if you looked at the equivalent circuit of a power transformer: -



\$L_P\$ and \$L_S\$ are inductances that don't couple between primary and secondary aka leakage inductance.


  I've never seen magnetization inductance calculation.


I've literally seen dozens and dozens - it's probably one of the first calculations you make when designing a transformer. You have the core material and dimensions and from that you can calculate inductance based on \$A_L\cdot N^2\$ where \$A_L\$ is a number that embodies all the core and dimensional data and \$N\$ is the number of turns.