mpt3sas: Fix static analyzer(coverity) tool identified defects

mpt3sas: Fix static analyzer(coverity) tool identified defects

BugLink: http://bugs.launchpad.net/bugs/1512221
1.Wrong size of argument is being passed
 The size of struct being passed as an argument to memset func and area of
 memory being pointed by an instance of struct in memset func should be of
 same structure type.
2.Dereference null return value
3.Array compared against '0'
 Check whether value pointed by particular index of an array is null or not
 in "if" statement.

Signed-off-by: Suganath prabu Subramani <suganath-prabu.subramani@avagotech.com>
Signed-off-by: Chaitra P B <chaitra.basappa@avagotech.com>
Reviewed-by: Tomas Henzl <thenzl@redhat.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
(cherry picked from commit dc2ed1660060a04ae9857047ace1169bddeb2ef6)
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>