The find_first_bit function will return the size passed to search
if the first set bit is not found. This patch adds the check in case
that happens as the return value would be used as the index in an array
and that would have caused the out-of-bounds access.

Detected by CoverityScan, CID 1295969 Out-of-bounds access
Signed-off-by: Lihong Yang <lihong.yang@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>