Staging: rdma: hfi1: Delete NULL check before vfree

The function vfree test whether the argument is NULL and return
immediately. SO NULL test is not needed before vfree.

Signed-off-by: Bhumika Goyal <bhumirks@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>