Locha is a Marathi word. However, it's also spoken in Hindi, especially in Mumbaiya Hindi, and has become quite like part of a slang, used quite commonly.
Ulfat, on the other hand, is a word that is Urdu and is used frequently in Urdu poetry, ranging from Ghalib and Mir's days to '90s Bollywood songs.
As far as I know, I have never seen the two words in one line, let alone join them to make one word. That's what Amitabh Bhattacharya just did.
As for the meanings, Locha means a problem, Ulfat means Love, and -e- is used in Urdu for the preposition 'of.' So locha-e-ulfat means The problem of love. And hence the line, Locha e ulfat ho gaya means that the problem of love is here!
For the Translation of entire song Locha-e-Ulfat, CLICK HERE.