vpu: decoder: added property for the minimum number of framebuffers

Signed-off-by: Carlos Rafael Giani <dv@pseudoterminal.org>
ipu: blitter: added function to check if any transformation is enabled

if gst_imx_ipu_blitter_are_transforms_enabled() returns FALSE, then
the only possible remaining transformations are those defined by the
src/sink caps

Signed-off-by: Carlos Rafael Giani <dv@pseudoterminal.org>
ipu: videotransform: passthrough mode no longer solely depends on the caps

if for example sink and src caps are identical, but rotation is enabled,
prior to this commit the element didn't do anything

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