serial: 8250_lpss: split LPSS driver to separate module

serial: 8250_lpss: split LPSS driver to separate module

The SoCs, such as Intel Braswell, have DesignWare UART IP. Split out the
support of such chips to a separate module which also will be used for Intel
Quark later.

The rationale to have the separate driver to be existing:
- Do not contaminate 8250_pci.c anymore with LPSS related quirks
- All of them are using same DMA engine and they are Designware IP which means
  that in the future we might share the code between 8250_dw.c and 8250_lpss.c
- It reduces the kernel memory footprint on non-X86 machines where 8250_pci.c
  is in use

Besides the split the driver also has been refactored, in particular a) the DMA
and port setup are separate functions, b) the two new structures lpss8250 and
lpss8250_board are introduced to keep necessary data instead of
pciserial_board, c) DMA parameters are passed to the DMA setup via mentioned
custom structure. Most of the changes are done due to the future support of
UART DMA on Intel Quark.

The Intel Quark UART DMA support is based on bits taking from BSP code
published by Intel earlier.

The driver does not use any specific power management. PCI core takes care of
the default behaviour during suspend and resume.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Tested-by: Bryan O'Donoghue <pure.logic@nexus-software.ie>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>