There are a number of places in the aic7xxx driver where a NULL check is
performed before a kfree(). However, kfree() already performs NULL checks
so this is unnecessary. Remove the checks.

Issue identified with Coccinelle.

Link: https://lore.kernel.org/r/20200403164712.49579-1-alex.dewar@gmx.co.ukSigned-off-by: Alex Dewar <alex.dewar@gmx.co.uk>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>