serial: core: clean up EXPORT_SYMBOLs

Some EXPORT_SYMBOLs are grouped at one location. Some follow functions
they export, but a newline is present before them. Fix all these and
move them where they belong.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20220124071430.14907-2-jslaby@suse.cz


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>