What do you call the "narrator" of lyric poem?

Quoting from here:

Persona as a literary term refers to the narrator or speaker of the poem, not to be confused with the author — a narrative voice other than the poet tells the entire poem. When the poet creates a character to be the speaker, that character is called the persona and the poet imagines what it is like to enter someone else’s personality. A good example of this is in Robert Browning’s “My Last Duchess”, where the persona is the Duke of Ferrara.

The term speaker is perhaps more appropriate when referring to a poem, as a narrator may be confused with either the person interpreting the poem, or the narrator of a novel. However, it always depends on how you intend to use the term.

The term is narrator. You don't need to look any further than that.

From NOAD:

narrator |ˈnarātər|
noun
a person who narrates something, esp. a character who recounts the events of a novel or narrative poem.

Sometimes people will refer to "the poet," but that is not really accurate, since the poem may not be intended to be spoken from the actual poet's perspective, but instead by a character or voice the poet creates. Sometimes the voice or character is referred to as "the speaker," especially in the case of dramatic monologues (e.g., Browning's "My Last Duchess").

You can call the narrator a persona.