net: atlantic: Use readx_poll_timeout() for large timeout

Commit
   8dcf2ad3 ("net: atlantic: add hwmon getter for MAC temperature")

implemented a read callback with an udelay(10000U). This fails to
compile on ARM because the delay is >1ms. I doubt that it is needed to
spin for 10ms even if possible on x86.

>From looking at the code, the context appears to be preemptible so using
usleep() should work and avoid busy spinning.

Use readx_poll_timeout() in the poll loop.

Fixes: 8dcf2ad3

 ("net: atlantic: add hwmon getter for MAC temperature")
Cc: Mark Starovoytov <mstarovoitov@marvell.com>
Cc: Igor Russkikh <irusskikh@marvell.com>
Signed-off-by: Sebastian Andrzej Siewior <sebastian@breakpoint.cc>
Acked-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: David S. Miller <davem@davemloft.net>