usb: gadget: udc: renesas_usb3: should fail if devm_phy_get() returns error

usb: gadget: udc: renesas_usb3: should fail if devm_phy_get() returns error

BugLink: http://bugs.launchpad.net/bugs/1790188
commit 0259068f63f23a665ded28647f2f9cdb6b20dc72 upstream.

This patch fixes an issue that this driver ignores errors other than
the non-existence of the device, f.e. a memory allocation failure
in devm_phy_get(). So, this patch replaces devm_phy_get() with
devm_phy_optional_get().

Reported-by: Simon Horman <horms+renesas@verge.net.au>
Fixes: 279d4bc64060 ("usb: gadget: udc: renesas_usb3: add support for generic phy")
Cc: <stable@vger.kernel.org> # v4.15+
Reviewed-by: Simon Horman <horms+renesas@verge.net.au>
Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>