pinctrl: pinctrl-single: Remove some unused fields in struct pcs_function

In "struct pcs_function", the 'pgnames' and 'npgnames' fields are unused.
This is a left-over from commit 571aec4d ("pinctrl: single: Use generic
pinmux helpers for managing functions");

Remove them.

Found with cppcheck, unusedStructMember.

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Message-ID: <a6b653642298d35b1e3656e9bfc6d1b322fbbe68.1712004518.git.christophe.jaillet@wanadoo.fr>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>