mei: hdcp: fix mei_hdcp_verify_mprime() input parameter

wired_cmd_repeater_auth_stream_req_in has a variable
length array at the end. we use struct_size() overflow
macro to determine the size for the allocation and sending
size.
This also fixes bug in case number of streams is > 0 in the original
submission. This bug was not triggered as the number of streams is
always one.

Fixes: c56967d6 (mei: hdcp: Replace one-element array with flexible-array member)
Fixes: 0a1af1b5 (misc/mei/hdcp: Verify M_prime)
Cc: <stable@vger.kernel.org> # v5.1+: c56967d6

 (mei: hdcp: Replace one-element array with flexible-array member)
Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Link: https://lore.kernel.org/r/20200818075406.2532605-1-tomas.winkler@intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>