IB/srp: Remove superfluous casts

A long time ago the data type int64_t was declared as long long
on x86 systems and as long on PPC systems. Today that data type
is declared as long long on all Linux architectures. This means
that the casts from uint64_t into unsigned long long are
superfluous. Remove these superfluous casts.

Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
Reviewed-by: Sagi Grimberg <sagig@mellanox.com>
Cc: Sebastian Parschauer <sebastian.riemer@profitbricks.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>