ab ke : 'This time'. (Platts p.1)
ye;Nhii;N is an archaic variant of yuu;N hii .
yuu;N : 'Thus, in this wise, in this manner; --just so, for no particular reason; without just ground, vainly, idly, causelessly, gratuitously; to please oneself'. (Platts p.1253)
The lover likes to wander around in madness and create a tumult, but this year, in the spring, so much weakness overpowered him that, oh Asad, he was not able to play his favored games.
For more on Ghalib's unpublished verses, see the discussion in {4,8x}. See also the overview index.
The grammar of the second line may seem somewhat confusing. But the semantic emphasis surely needs to fall on baras , which after all is an unexpected word, and is placed in the crucial and powerful rhyme-word position, at the very end of the verse.
The line thus, at the last moment, punchily conveys the idea that this time, the springtime was-- since the mad lover was too weak to create his desired turmoil-- a whole 'year' long. The colloquial yuu;N hii has a range of meanings (see the definition above), but is ultimately almost impossible to capture in English.
Compare {152,1}, which similarly plays with the duration of a 'year'.
Asi:
Oh Asad, weakness made us so helpless and so powerless that we were not even able to create an intoxicated commotion, and we also refrained from the tumult of madness. The whole year of this spring [Asi's text has ab kii] passed {casually / 'like this'}.
== Asi, p. 160