mfd: intel_soc_pmic_bxtwc: Fix usbc interrupt

The wcove USB Type-C driver is currently being flooded with
interrupts that are not targeted to it. The reason for that
is because all CHRG first level interrupts are mapped to it.
This fixes the issue by introducing separate irq for the
usbc device, and mapping only USB Type-C PHY interrupts to
it.

Fixes: 9c6235c8 ("mfd: intel_soc_pmic_bxtwc: Add bxt_wcove_usbc device")
Signed-off-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>