drivers: pinctrl: make ti_k3 multi-instance

Some devices have multiple pinctrl regions; for instance, main pinctrl and
mcu pinctrl. Currently there can only be a single pinctrl instance picked
form a DT label. This patch makes the pinctrl driver initialise one
instance for each node with correct compatible string.

Signed-off-by: Amneesh Singh <a-singh7@ti.com>