pwm: stm32: Add check for clk_enable()

Add check for the return value of clk_enable() to catch the potential
error.

Fixes: 19f1016e ("pwm: stm32: Fix enable count for clk in .probe()")
Signed-off-by: Mingwei Zheng <zmw12306@gmail.com>
Signed-off-by: Jiasheng Jiang <jiashengjiangcool@gmail.com>
Link: https://lore.kernel.org/r/20241215224752.220318-1-zmw12306@gmail.com


Signed-off-by: Uwe Kleine-König <ukleinek@kernel.org>