tests: Resort check-qtest entries in Makefile.include

The rather random list of check-qtest-xxx entries caused some
confusion in the past, where to use "=" and where to use "+="
(see commits 0ccac16f59462b8e2b9afbc1 and 1f5c1cfbaec0792cd2e5da
for example).
Sorting the check-qtest-xxx entries by architecure instead and
using some empty lines inbetween should help to ease this
situation a little bit, so that it is hopefully now obvious
that new tests should be added with "+=" instead of "=".
While we are at it, this patch also comments out two of the
"gcov-files-..." lines since the corresponding m48t59-test is
disabled for sparc and sparc64, too.

Signed-off-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
