libertas: fix improper return value

Function lbs_cmd_802_11_sleep_params() always return 0, even if the call
to lbs_cmd_with_response() fails. In this case, the parameter @sp will
keep uninitialized. Because the return value is 0, its caller (say
lbs_sleepparams_read()) will not detect the error, and will copy the
uninitialized stack memory to user sapce, resulting in stack information
leak. To avoid the bug, this patch returns variable ret (which takes
the return value of lbs_cmd_with_response()) instead of 0.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=188451



Signed-off-by: Pan Bian <bianpan2016@163.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>