usb: host: Fix smask_out array access to a non verified index

Fix code quality issues found by the automatic checking tool.
Verify hs_transfers before accessing the smask_out array
in this index.

Change-Id: I724278f4972c471431993270d3962230b1c69791
CRs-Fixed: 566927
Signed-off-by: Danny Segal <dsegal@codeaurora.org>
Signed-off-by: Maya Erez <merez@codeaurora.org>