[SERIAL] mark several serial tables const

This patch marks a few serial data structures const, moving them to
.rodata where they won't false-share cachelines with things that get
written to.

Signed-off-by: Arjan van de Ven <arjan@infradead.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

diff --cc drivers/serial/8250.c
Simple merge

diff --cc drivers/serial/8250_pci.c
Simple merge

diff --cc drivers/serial/serial_core.c
Simple merge

diff --cc drivers/serial/serial_cs.c
Simple merge