linker: section_tags: fix missing include

If using `<zephyr/linker/section_tags.h>` without including
`zephyr/linker/sections.h` as well, we get a warning an the linker fails
to place the data in the desired section.

Signed-off-by: Martin Stumpf <finomnis@gmail.com>
(cherry picked from commit 77eafac1)