phy/micrel: Add suspend/resume support to Micrel PHYs

All supported Micrel PHYs implement the standard "power down" bit 11 of BMCR,
so this patch adds support using the generic genphy_{suspend,resume} functions.

Signed-off-by: Patrice Vilchez <patrice.vilchez@atmel.com>
[b.brezillon@overkiz.com: adapt to newer kernel and generalize to other phys]
Signed-off-by: Boris BREZILLON <b.brezillon@overkiz.com>
[nicolas.ferre@atmel.com: commit message modification]
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Cc: David J. Choi <david.choi@micrel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>