usb: phy: samsung: Select common driver part implicitly

Since phy-samsung-usb library can be used only by phy-samsung-usb2 and
phy-samsung-usb3 drivers, there is no need to give explicit control over
its Kconfig symbol.

This patch makes CONFIG_SAMSUNG_USBPHY symbol hidden and selected
implicitly by CONFIG_SAMSUNG_USB2PHY and CONFIG_SAMSUNG_USB3PHY.
Signed-off-by: Tomasz Figa <t.figa@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>

drivers/usb/phy/Kconfig

@@ -86,7 +86,7 @@ config OMAP_USB3
 	  on/off the PHY.
 
 config SAMSUNG_USBPHY
-	tristate "Samsung USB PHY Driver"
+	tristate
 	help
 	  Enable this to support Samsung USB phy helper driver for Samsung SoCs.
 	  This driver provides common interface to interact, for Samsung USB 2.0 PHY