rtc: st-lpc: Release some resources in st_rtc_probe() in case of error

If an error occurs after clk_get(), the corresponding resources should be
released.

Use devm_clk_get() to fix it.

Fixes: b5b2bdfc ("rtc: st: Add new driver for ST's LPC RTC")
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Link: https://lore.kernel.org/r/866af6adbc7454a7b4505eb6c28fbdc86ccff39e.1686251455.git.christophe.jaillet@wanadoo.fr


Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>