soc: samd5x: xosc32 initialization - 8 seconds start-up time

[nandojve]

Discussed in #79883

^{Originally posted by wag-thom October 11, 2024}
The commit 58a54e3 (@nandojve) changed in soc_samd5x.c in the osc32k_init() function the register configuration for the external 32K crystal.

zephyr/soc/atmel/sam0/common/soc_samd5x.c

Line 27 in e40fa89

| OSC32KCTRL_XOSC32K_STARTUP(6) | OSC32KCTRL_XOSC32K_CGM_XT;

Previously, the start-up value was set to 7 - which was a reserved according to the datasheet.
Now it is set to 6 - which translates to a start-up time of 8 seconds. I don't think this is a sensible value for most users.

I would suggest to either:

• change the value to 0 (Which will result in the same behavior as before the change - I get the same start-up time with 0 or 7)
• or let the user set the value with some Kconfig option