nfc: s3fwrn5: use devm_clk_get_optional_enabled() helper

Because we enable the clock immediately after acquiring it in probe,
we can combine the 2 operations and use devm_clk_get_optional_enabled()
helper.

Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: David S. Miller <davem@davemloft.net>