phy: tegra: xusb: Make USB_CONN_GPIO select conditional on GPIOLIB

phy: tegra: xusb: Make USB_CONN_GPIO select conditional on GPIOLIB

kconfiglint reports:

  K006: config PHY_TEGRA_XUSB selects USB_CONN_GPIO which depends on
        GPIOLIB, but PHY_TEGRA_XUSB does not depend on GPIOLIB
  K002: config PHY_TEGRA_XUSB selects visible symbol USB_CONN_GPIO
        which has dependencies

USB_CONN_GPIO was introduced in commit 4602f3bff266 ("usb: common: add USB
GPIO based connection detection driver") with a hard dependency on GPIOLIB,
since it needs GPIO pins to detect USB cable connection state.

Commit f67213cee2b3 ("phy: tegra: xusb: Add usb-role-switch support") added
`select USB_CONN_GPIO` to PHY_TEGRA_XUSB to support USB role switching via
GPIO-based detection. At that time, PHY_TEGRA_XUSB depended only on
`ARCH_TEGRA`, and both the ARM32 and ARM64 ARCH_TEGRA Kconfig definitions
select GPIOLIB, so the missing explicit GPIOLIB guard was not a functional
problem — GPIOLIB is always available when ARCH_TEGRA is enabled.

Later, commit 0d5c9bc7c680 ("phy: tegra: Select USB_COMMON for
usb_get_maximum_speed()") added `depends on USB_SUPPORT` but still did not
address the GPIOLIB gap.

The select can force USB_CONN_GPIO on without its GPIOLIB dependency being
satisfied if the Kconfig dependencies were ever restructured. Make the
select conditional with `select USB_CONN_GPIO if GPIOLIB` to make the
dependency explicit. This mirrors how other drivers handle optional
GPIO-dependent selects throughout the kernel.

Assisted-by: Claude:claude-opus-4-6 kconfiglint
Signed-off-by: Sasha Levin <sashal@kernel.org>
Link: https://patch.msgid.link/20260426000309.54959-1-sashal@kernel.org
Signed-off-by: Vinod Koul <vkoul@kernel.org>