phy: qcom-usb-hs: Add depends on EXTCON

We get the following compile errors if EXTCON is enabled as a
module but this driver is builtin:

drivers/built-in.o: In function `qcom_usb_hs_phy_power_off':
phy-qcom-usb-hs.c:(.text+0x1089): undefined reference to `extcon_unregister_notifier'
drivers/built-in.o: In function `qcom_usb_hs_phy_probe':
phy-qcom-usb-hs.c:(.text+0x11b5): undefined reference to `extcon_get_edev_by_phandle'
drivers/built-in.o: In function `qcom_usb_hs_phy_power_on':
phy-qcom-usb-hs.c:(.text+0x128e): undefined reference to `extcon_get_state'
phy-qcom-usb-hs.c:(.text+0x12a9): undefined reference to `extcon_register_notifier'

so let's mark this as needing to follow the modular status of
the extcon framework.

Fixes: 9994a338 e2427b09 (phy: Add support for Qualcomm's USB HS phy")
Signed-off-by: Stephen Boyd <stephen.boyd@linaro.org>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>