rtc: asm9260: add the missed check for devm_clk_get

The driver misses a check for devm_clk_get().
Add the check to fix it.

Signed-off-by: Chuhong Yuan <hslester96@gmail.com>
Link: https://lore.kernel.org/r/20191214074528.16806-1-hslester96@gmail.com


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