Fix disconnection problem for HTML5 SOL

When using Legacy Boot Mode in Intel platforms, HTML5 SOL console will
be disconnected when host start.
When host start, BIOS will send some non UTF-8 data to SOL console,
then SOL console will be disconnected. Changing to binary format can
make WSS protocol work correctly with non UTF-8 data.

Change-Id: I9a440220f16eb07d800dc291897ab3106cd40c32
Signed-off-by: Cheng C Yang <cheng.c.yang@linux.intel.com>