linuxkpi: Move `release_pages()` to linux_page.c

[dumbbell]

Summary

We want to avoid putting code managing memory in inline functions in the future.

This is part of the update of DRM drivers to Linux 6.7. This is a follow-up to D48743.

Sponsored by: The FreeBSD Foundation

[wulf]

sys/compat/linuxkpi/common/src/linux_page.c

180

Please add lkpi_ or linuxkpi_ prefix with corresponding #define to not pollute namespace

[dumbbell]

Rename release_pages() to linux_release_pages() to address @wulf concern.