[media] vidioc-g-tuner.rst: improve documentation for tuner type

The tuner type table misses descriptions for each type. While
most of stuff are obvious, the two SDR definitions aren't.

So, add descriptions to all of them.
Signed-off-by: NMauro Carvalho Chehab <mchehab@s-opensource.com>

Documentation/media/uapi/v4l/vidioc-g-tuner.rst

@@ -260,7 +260,7 @@ To change the radio frequency the
 .. flat-table:: enum v4l2_tuner_type
     :header-rows:  0
     :stub-columns: 0
-    :widths:       3 1 4
+    :widths:       3 1 6
 
 
     -  .. row 1
@@ -269,7 +269,7 @@ To change the radio frequency the
 
        -  1
 
-       -
+       - Tuner supports radio
 
     -  .. row 2
 
@@ -277,7 +277,7 @@ To change the radio frequency the
 
        -  2
 
-       -
+       - Tuner supports analog TV
 
     -  .. row 3
 
@@ -285,7 +285,8 @@ To change the radio frequency the
 
        -  4
 
-       -
+       - Tuner controls the A/D and/or D/A block of a
+	 Sofware Digital Radio (SDR)
 
     -  .. row 4
 
@@ -293,8 +294,7 @@ To change the radio frequency the
 
        -  5
 
-       -
-
+       - Tuner controls the RF part of a Sofware Digital Radio (SDR)
 
 
 .. _tuner-capability: