pinctrl: armada-37xx: Use int type to store negative error codes

In armada_37xx_gpio_direction_output(), the 'ret' variable might store
the negative error codes returned by regmap_update_bits(), and in
armada_37xx_edge_both_irq_swap_pol(), the 'ret' variable directly
stores -1, so the type of the 'ret' variable needs to be changed to
int in both cases.

No effect on runtime.

Signed-off-by: Qianfeng Rong <rongqianfeng@vivo.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>