libvirt-domain.h: Fix enum description placement

libvirt-domain.h: Fix enum description placement

There are only two acceptable places for describing enum values.
It's either:

    typedef enum {
        /* Some long description. Therefore it's placed before
         * the value. */
        VIR_ENUM_A_VAL = 1,
    } virEnumA;

or:

    typedef enum {
        VIR_ENUM_B_VAL = 1, /* Some short description */
    } virEnumB;

However, during review of a patch sent upstream I realized that
is not always the case. I went through all the public header
files and identified all the offenders. Luckily there were just
two of them.

Yes, this makes our HTML generated documentation broken, but
that's bug of the generator. Our header files shouldn't be forced
to use something we don't want to.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>