serial: sh-sci: Fix init data attribute for struct 'port_cfg'

The __init attribute is meant to mark functions, use __initdata instead
for the data structure.

This fixes the following error when building with clang:

drivers/tty/serial/sh-sci.c:3247:15: error: '__section__' attribute only
  applies to functions, methods, properties, and global variables
    static struct __init plat_sci_port port_cfg;

Signed-off-by: Matthias Kaehlcke <mka@chromium.org>
Reviewed-by: Guenter Roeck <groeck@chromium.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>