Remove erroneous semicolons after Q_DECLARE_* macros

Some of these declarations had habitual semicolons at the end,
which would fail when compiling with -Werror,-Wextra-semi.

Change-Id: I8dd73462fc1c10b0bb746fbfc3281d9cce36e5fc
Reviewed-by: Michael Brüning <michael.bruning@theqtcompany.com>