libata: Remove FIXME comment in atapi_eh_request_sense

Remove the FIXME comment in  atapi_eh_request_sense () asking whether
memset of sense buffer is necessary.  The buffer may be partially or
fully filled by the device.  We want it to be cleared.

Signed-off-by: Nicholas Krause <xerofoify@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>