[media] v4l2-mc.h: fix yet more compiler errors

The newly added functions have an extra semicolon, which
prevents compilation, and they need to be marked inline:

In file included from ../include/media/tuner.h:23:0,
                 from ../drivers/media/tuners/tuner-simple.c:10:
../include/media/v4l2-mc.h:233:1: error: expected identifier or '(' before '{' token

Remove spurious return, remove copy-and-pasted semi-colons, add static
inline.

Fixes: a77bf704 ("v4l2-mc.h: Add stubs for the V4L2 PM/pipeline routines")

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>