pinctrl: eswin: Fix unsigned comparison to less than zero issue

The u32 variable voltage is being compared to less than zero and
this can never be true. Fix this by making voltage an int type which
is the same type as the return from the call to regulator_get_voltage.

Fixes: 5b797bcc ("pinctrl: eswin: Add EIC7700 pinctrl driver")
Signed-off-by: Colin Ian King <colin.i.king@gmail.com>
Link: https://lore.kernel.org/20250623222004.280928-1-colin.i.king@gmail.com


Signed-off-by: Linus Walleij <linus.walleij@linaro.org>