drivers: phy: add generic PHY framework

The PHY framework provides a set of APIs to control a PHY. This API is
derived from the linux version of the generic PHY framework.
Currently the API supports init(), deinit(), power_on, power_off() and
reset(). The framework provides a way to get a reference to a phy from the
device-tree.

Signed-off-by: Jean-Jacques Hiblot <jjhiblot@ti.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

include/dm/uclass-id.h

@@ -56,6 +56,7 @@ enum uclass_id {
 	UCLASS_PCH,		/* x86 platform controller hub */
 	UCLASS_PCI,		/* PCI bus */
 	UCLASS_PCI_GENERIC,	/* Generic PCI bus device */
+	UCLASS_PHY,		/* Physical Layer (PHY) device */
 	UCLASS_PINCONFIG,	/* Pin configuration node device */
 	UCLASS_PINCTRL,		/* Pinctrl (pin muxing/configuration) device */
 	UCLASS_PMIC,		/* PMIC I/O device */