Bluetooth: btmtk: remove extra copy in cmd array init

Bluetooth: btmtk: remove extra copy in cmd array init

In btmtk_setup_firmware_79xx, the data length indicated by wmt_params.dlen
in the cmd buffer is MTK_SEC_MAP_NEED_SEND_SIZE + 1. Except for the first
byte, the remaining length is MTK_SEC_MAP_NEED_SEND_SIZE. memcpy copied one
more byte to cmd + 1 than the remaining length. Align the length passed to
memcpy to avoid exceeding current section map.

Signed-off-by: Jiajia Liu <liujiajia@kylinos.cn>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>