[SCSI] bnx2i: Adjust sq_size module parametr to power of 2 only if a non-zero value is specified

This issue was discovered during 10G iscsi testing

Default value of 'sq_size' module parameter is '0' which means driver
should use predefined SQ queue size when setting up iscsi connection.

roundup_pow_of_two(0) results in '1' and forces driver to setup
connections with send queue size of '1' and results in lower
performance as well

Signed-off-by: Anil Veerabhadrappa <anilgv@broadcom.com>
Reviewed-by: Mike Christie <michaelc@cs.wisc.edu>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>