V4L/DVB (5736): Add V4L2_FBUF_CAP/FLAG_LOCAL/GLOBAL_INV_ALPHA

Michael Schimek requested the addition of inverted alpha framebuffer
caps/flags to support such hardware.
'Normal' alpha uses this formula to mix the framebuffer and video:
output = fb pixel * fb alpha + video pixel * (1 - fb alpha)
and the 'inverted' alpha uses this formula:
output = fb pixel * (1 - fb alpha) + video pixel * fb alpha

Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>

include/linux/videodev2.h

@@ -615,12 +615,16 @@ struct v4l2_framebuffer
 #define V4L2_FBUF_CAP_BITMAP_CLIPPING	0x0008
 #define V4L2_FBUF_CAP_LOCAL_ALPHA	0x0010
 #define V4L2_FBUF_CAP_GLOBAL_ALPHA	0x0020
+#define V4L2_FBUF_CAP_LOCAL_INV_ALPHA	0x0040
+#define V4L2_FBUF_CAP_GLOBAL_INV_ALPHA	0x0080
 /*  Flags for the 'flags' field. */
 #define V4L2_FBUF_FLAG_PRIMARY		0x0001
 #define V4L2_FBUF_FLAG_OVERLAY		0x0002
 #define V4L2_FBUF_FLAG_CHROMAKEY	0x0004
 #define V4L2_FBUF_FLAG_LOCAL_ALPHA	0x0008
 #define V4L2_FBUF_FLAG_GLOBAL_ALPHA	0x0010
+#define V4L2_FBUF_FLAG_LOCAL_INV_ALPHA	0x0020
+#define V4L2_FBUF_FLAG_GLOBAL_INV_ALPHA	0x0040
 
 struct v4l2_clip
 {