Bluetooth: btnxpuart: Remove check for CTS low after FW download

This removes the unnecessary check for CTS low after FW download.

After FW download is complete, the CTS line is already seen low.
It becomes high after 2 msec, and low again after FW initialization
is complete.
This makes the current check for CTS low redundant.

This removes the wait for CTS low section and increase delay to
1200msec instead, which is sufficiant for all NXP chipsets to
initialize FW.

Signed-off-by: Neeraj Sanjay Kale <neeraj.sanjaykale@nxp.com>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>