pinctrl: mcp23s08: Rename and change function that wraps regmap_update_bits()

pinctrl: mcp23s08: Rename and change function that wraps regmap_update_bits()

The semantic of mcp_set_mask() was surprising to me when I first read
that driver. So it was unexpected that in the call

	mcp_set_mask(mcp, MCP_OLAT, mask, value);

value was a bool. Make the function a thinner wrapper around
regmap_update_bits() and rename it to also have a similar name.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Link: https://lore.kernel.org/r/20230324164957.485924-2-u.kleine-koenig@pengutronix.de
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>