media: tegra-cec: reset rx_buf_cnt when start bit detected
If a start bit is detected, then reset the receive buffer counter to 0.
This ensures that no stale data is in the buffer if a message is
broken off midstream due to e.g. a Low Drive condition and then
retransmitted.
The only Rx interrupts we need to listen to are RX_REGISTER_FULL (i.e.
a valid byte was received) and RX_START_BIT_DETECTED (i.e. a new
message starts and we need to reset the counter).
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com> Cc: <stable@vger.kernel.org> # for v4.15 and up Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>