serial: 8250_dwlib: move DesignWare register definitions to header

serial: 8250_dwlib: move DesignWare register definitions to header

Move the DW_UART_* register offsets and CPR bit/field definitions from
8250_dwlib.c into 8250_dwlib.h so they can be shared by 8250_dw and
8250_dwlib users.

Add an include guard for 8250_dwlib.h.

Signed-off-by: Jia Wang <wangjia@ultrarisc.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://patch.msgid.link/20260429-ultrarisc-serial-v7-1-e475cce9e274@ultrarisc.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>