ath6kl: add padding to firmware log records

firmware debug utility expects firmware log record size
to be 1500 bytes. This patch ensures that the
firmware record will be exactly 1500 bytes.

kvalo: remove trailing space

Signed-off-by: Etay Luz <eluz@qca.qualcomm.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>