net: ethernet: ti: am65-cpsw/cpts: Add suspend/resume helpers

CPTS looses context on suspend (e.g. on AM62).
Provide suspend/resume hooks in CPTS driver. These will be
invoked by CPSW driver if CPTS was instantiated by CPSW.

Signed-off-by: Roger Quadros <rogerq@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>