usb: dwc2/gadget: fix phy initialization sequence

In the Generic PHY Framework a NULL phy is considered to be a valid phy
thus the "if (hsotg->phy)" check does not give us the information whether
the Generic PHY Framework is used.

In addition to the above this patch also removes phy_init from probe and
phy_exit from remove. This is not necessary when init/exit is done in the
s3c_hsotg_phy_enable/disable functions.

Signed-off-by: Kamil Debski <k.debski@samsung.com>
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Robert Baldyga <r.baldyga@samsung.com>
Cc: stable <stable@vger.kernel.org> # 3.16
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>