imx8mp-pinctrl handles drive-strength and slew-rate incorrectly

[voltamund]

Describe the bug

Target platform: MIMX8MM6 Cortex M4
I think with the changes in #75083 drive-strength and slew-rate are not correctly handled anymore.

drive-strength = "x6" should result in 11x but it actually results in 011. Something similar also happens for slew-rate. Before this change the enum values were also incorrect (not according to the nxp reference manual) but somehow resulted in the correct register values, i.e. 40-ohm resulted in 11x.

Expected behavior

Device tree values for drive-strength and slew-rate result in correct register values.

Environment (please complete the following information):

• OS: Linux
• Toolchain: zephyr-sdk-0.16.8
• Zephyr Version 3.7.0