extcon: palmas: Fix boot up state of VBUS when using GPIO detection

If USB cable is connected prior to boot, we don't get any interrupts
so we must manually check the VBUS state and report it during probe.
If we don't do it then USB controller will never know that peripheral
cable was connected till the user unplugs and replugs the cable.

Fixes: b7aad8e2 ("extcon: palmas: Add the support for VBUS detection by using GPIO")
Cc: stable@vger.kernel.org
Signed-off-by: Roger Quadros <rogerq@ti.com>
Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>