gpio: acpi: Align acpi_find_gpio() with DT version

By some reason acpi_find_gpio() and acpi_gpio_count() have compared
connection ID to "gpios" when tries to check if suffix is needed or not.

Don't do any assumptions about what connection ID can be and, when defined,
use it only with suffix as it's done in the device tree version.

Reviewed-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Tested-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>