AO4 BIOS updated - INSP 7520

A04 BIOS released for INSP 7520 system, this would help fix the BSOD issues.

http://www.dell.com/support/drivers/us/en/19/DriverDetails/DriverFileFormats/Product/inspiron-15r-se-7520?DriverId=Y5NFG&FileId=2999230843&urlProductCode=False