gma500: mdfld_dsi_dpi_mode_set() do not corrupt DSPSTRIDE

The proper stride value set in mdfld__intel_pipe_set_base().

TODO: move tc35876x support to separate driver and get rid of all
if (mdfld_get_panel_type(dev, pipe) == TC35876X) { ... }

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>