net: ena: Add more information on TX timeouts

The function responsible for polling TX completions might not receive
the CPU resources it needs due to higher priority tasks running on the
requested core.

The driver might not be able to recognize such cases, but it can use its
state to suspect that they happened. If both conditions are met:

- napi hasn't been executed more than the TX completion timeout value
- napi is scheduled (meaning that we've received an interrupt)

Then it's more likely that the napi handler isn't scheduled because of
an overloaded CPU.
It was decided that for this case, the driver would wait twice as long
as the regular timeout before scheduling a reset.
The driver uses ENA_REGS_RESET_SUSPECTED_POLL_STARVATION reset reason to
indicate this case to the device.

This patch also adds more information to the ena_tx_timeout() callback.
This function is called by the kernel when it detects that a specific TX
queue has been closed for too long.

Signed-off-by: Shay Agroskin <shayagr@amazon.com>
Signed-off-by: David Arinzon <darinzon@amazon.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>