ARM: S3C64XX: serial: Fix section mismatch warning

Rename the structure to avoid the following warning:

WARNING: vmlinux.o(.data+0x11ef4): Section mismatch in reference from the variable
s3c6400_serial_drv to the function .devexit.text:s3c24xx_serial_remove()
The variable s3c6400_serial_drv references
the function __devexit s3c24xx_serial_remove()
If the reference is valid then annotate the
variable with __exit* (see linux/init.h) or name the variable:
*driver, *_template, *_timer, *_sht, *_ops, *_probe, *_probe_one, *_console,

Signed-off-by: Ramax Lo <ramaxlo@gmail.com>
Signed-off-by: Ben Dooks <ben-linux@fluff.org>