drivers: mfd: add new driver "mfd_adp5585"

Add mfd_adp5585 and gpio_adp5585 driver. This driver enables ADP5585
as an GPIO expander.
This chip is used as an GPIO expander on i.MX93 EVK. GPIO pinctrl,
read/write and interrupt is supported.
Note that ADP5585 has 2 GPIO banks with 5 pins each. The driver combines
two group into a 16-bit port. Index 0~4 correspond to R0~R4 lines, index
8~12 correspond to C0~C4 lines. Index 5~7 is reserved unavailable.

Signed-off-by: Chekhov Ma <chekhov.ma@nxp.com>