pmic: pca9450: Add PCA9450C compatible string

pmic: pca9450: Add PCA9450C compatible string

Add DT compatible string for PCA9450C PMIC. This is a variant of the
PCA9450 PMIC with 6 A dual-phase buck regulator and 3 A buck regulator,
and is software-wise compatible with the PCA9450B. This variant of the
PCA9450 is designed for use as companion PMIC for i.MX8MP.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Fabio Estevam <festevam@denx.de>
Cc: Peng Fan <peng.fan@nxp.com>
Cc: Stefano Babic <sbabic@denx.de>
Reviewed-by: Fabio Estevam <festevam@denx.de>
Reviewed-by: Jaehoon Chung <jh80.chung@samsung.com>