scsi: aic7xxx: Use kzalloc() instead of kmalloc()+memset()

There are a couple of places where kzalloc() could be used directly instead
of calling kmalloc() then memset(). Replace them.

Link: https://lore.kernel.org/r/20200403163611.46756-1-alex.dewar@gmx.co.uk


Signed-off-by: Alex Dewar <alex.dewar@gmx.co.uk>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>