megaraid_sas: Fix reset_mutex leak

The following patch for megaraid_sas fixes a reset_mutex leak in megasas_reset_fusion().

Signed-off-by: Adam Radford <aradford@gmail.com>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>