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;