Input: cyttsp - fix memcpy size param

memcpy param is wrong because of offset in bl_cmd, this may corrupt the
stack which may cause a crash.

Tested-by: Ferruh Yigit <fery@cypress.com> on TMA300-DVK
Signed-off-by: Ferruh Yigit <fery@cypress.com>
Acked-by: Javier Martinez Canillas <javier@dowhile0.org>
Cc: stable@vger.kernel.org
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>