[media] docs-rst: fix dmx bad cross-references

Some structs are pointed via the typedef. As we replaced
those references, fix them.
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

Documentation/media/uapi/dvb/dmx-get-caps.rst

@@ -15,7 +15,7 @@ DMX_GET_CAPS
 Synopsis
 --------
 
-.. c:function:: int ioctl(fd, DMX_GET_CAPS, dmx_caps_t *caps)
+.. c:function:: int ioctl(fd, DMX_GET_CAPS, struct dmx_caps *caps)
     :name: DMX_GET_CAPS
 
 Arguments
@@ -25,7 +25,7 @@ Arguments
     File descriptor returned by :c:func:`open() <dvb-dmx-open>`.
 
 ``caps``
-    Undocumented.
+    Pointer to struct :c:type:`dmx_caps`
 
 
 Description
@@ -33,7 +33,6 @@ Description
 
 .. note:: This ioctl is undocumented. Documentation is welcome.
 
-
 Return Value
 ------------
 

Documentation/media/uapi/dvb/dmx-set-source.rst

@@ -15,7 +15,7 @@ DMX_SET_SOURCE
 Synopsis
 --------
 
-.. c:function:: int ioctl(fd, DMX_SET_SOURCE, dmx_source_t *src)
+.. c:function:: int ioctl(fd, DMX_SET_SOURCE, struct dmx_source *src)
     :name: DMX_SET_SOURCE