tcmu:fix error using the return value of function  tcmu_get_dev_max_xfer_length
tcmu:fix error using the return value of function  tcmu_get_dev_max_xfer_length

The return value of fuction tcmu_get_dev_max_xfer_len is number of sector, but some functions used it as data size, for example handle_writesam and handle_format_unit functions.

Signed-off-by: tangwenji <ad0e6531e466391ac7606aff432ef2be0306b52b@zte.com.cn>

open-iscsi/tcmu-runner,agrover/tcmu-runner,open-iscsi/tcmu-runner