EMERGING MARKETS-Latam stocks flat; Brazil rises on OGX, Rossi

* Banks, commodities weigh on Bovespa * Meatpackers gain after JBS earnings beat expectations * Brazil Bovespa up 0.49 pct, Mexico IPC flat By Asher Levine and Danielle Assalve SAO PAULO, May 15 (Reuters) - Brazilian stocks edged up on Wednesday, despite disappointing first-quarter results from Banco do Brasil and a drop in iron ore producer Vale, with the index boosted by gains in troubled oil company OGX and homebuilder Rossi Residencial. Both Mexico's IPC index and Chile