drivers: pinctrl: max32: fix correct configuring drive strength

This commit fixes configuring pin drive strength in pinctrl driver.
Previously, there was a mismatch while filling pincfg and checking
pincfg drive strength field. This fix simplifies the operation and
avoids gpio driver header dependency.

Signed-off-by: Mert Ekren <mert.ekren@analog.com>
Co-Authored-By: Sadik Ozer <sadik.ozer@analog.com>