Add mayfail bool parameter to module loading functions.  Set it to true
for module_load_qom_all() because device modules might not load into all
system emulation variants.  qemu-system-s390x for example will not load
qxl because it lacks vga support.  Makes "make check" less chatty.

Drop module_loaded_qom_all check in module_load_qom_one to make sure we
see errors for explicit load requests, i.e. module_load_qom_one("qxl")
failing will log an error no matter whenever module_load_qom_all() was
called before or not.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Message-id: 20200923091217.22662-1-kraxel@redhat.com