wil6210: increase timeout for the "echo" command

Sometimes it takes for the firmware more than 20ms to
react on "echo" command after reset. Increase timeout
from 20 to 50ms

Signed-off-by: Vladimir Kondratiev <qca_vkondrat@qca.qualcomm.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>