serial: sh-sci: Use private port ID

New port types cannot be added in serial_core.h, which is shared with
userspace.
In order to support new port types, the coming new ones will have
BIT(7) set in the id value, and in this case, uartport->type is
set to PORT_GENERIC.
This commit therefore changes all the places where the port type is
read, by not relying on uartport->type but on the private
value stored in struct sci_port.

Signed-off-by: Thierry Bultel <thierry.bultel.yh@bp.renesas.com>
Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/20250630202323.279809-5-prabhakar.mahadev-lad.rj@bp.renesas.com


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