pinctrl: Add an API to get the pinctrl pins if initialized

Add an API to get the pinctrl pins if it was initialized before driver
probed. This API will be used in I2C core to get the device pinctrl
information for recovery state change.

Signed-off-by: Hanna Hawa <hhhawa@amazon.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Wolfram Sang <wsa@kernel.org>