subsys: greybus: remove qsort implementation

[cfriedt]

qsort(3) became part of that standard C library with C99. Should probably be added to Zephyr's minimal libc implementation. I can't recall if Zephyr's newlib includes qsort() atm.

[cfriedt]

Added zephyrproject-rtos/zephyr#31107

[cfriedt]

There was an existing issue for this already at zephyrproject-rtos/zephyr#28896.

Zephyr has a fix in zephyrproject-rtos/zephyr#39980.

Would be great if that fix could make it into LTS.

I would very much like to rebase on v2.7-branch.

[cfriedt]

Again, although qsort is in LTS, the GPIO direction feature likely will not be backported. May need to revisit #70 and potentially pin to the upcoming 3.2 release.