Bluetooth HAL: Add missing retry logic to the H4Protocol::Send()

H4Protocol::Send function occasionally encountered errors such as "Error in
writing to UART (Try again),"indicating incomplete writes.

To address this, retry logic was added to handle scenarios where the write()
call couldn't transfer all the bytes in a single system call, ensuring
remaining bytes are sent successfully. This change introduces the necessary
retry mechanism to the function.

Bug: 380704157
Test: Bluetooth profile test : OPP, PAN

Change-Id: I481b88b1c1eeca5e89b884424ebcb7fde7232ded