IB/srp: Always initialize use_fast_reg and use_fmr

Avoid that mapping fails due to use_fast_reg != 0 or use_fmr != 0
if both member variables should be zero (if never_register == 1 or
if neither FMR nor FR is supported). Remove an initialization that
became superfluous due to changing a kmalloc() into a kzalloc()
call.

Fixes: 509c5f33 ("IB/srp: Prevent mapping failures")
Cc: Sagi Grimberg <sai@grimberg.m>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Laurence Oberman <loberman@redhat.com>
Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
Reviewed-by: Leon Romanovsky <leonro@mellanox.com>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Doug Ledford <dledford@redhat.com>