tests/qtest: Do not run lsi53c895a test if device is not present

tests/qtest: Do not run lsi53c895a test if device is not present

The tests are built once for all the targets, so as long as one QEMU
binary is built with CONFIG_LSI_SCSI_PCI=y, this test will
run. However some binaries might not include the device. So check this
again in runtime.

Signed-off-by: Fabiano Rosas <farosas@suse.de>
Message-Id: <20230208194700.11035-3-farosas@suse.de>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>
(cherry picked from commit dee66bc9691a0d5e8337c24b5cf303f46293df76)
(Mjt: pick this trivial focused fix up for 7.2.x so that subsequent change(s) in this area apply cleanly)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>