common: add mapping_flags member to GstImxPhysMemory

In GStreamer, it is possible to map the same memory block multiple times,
but the flags must be identical. This is useful for derived classes to
invalidate/clean caches, define mapping modes etc.

Signed-off-by: Carlos Rafael Giani <dv@pseudoterminal.org>
ipu: Define memory protection based on the value of "flags"

Signed-off-by: Carlos Rafael Giani <dv@pseudoterminal.org>
g2d: introduce cacheable DMA buffers and invalidate/clean caches as needed

Signed-off-by: Carlos Rafael Giani <dv@pseudoterminal.org>