kernel-doc: Remove $decl_type='type name' hack

kernel-doc: Remove $decl_type='type name' hack

The $decl_type='type name' hack makes it impossible to document
macros with uppercase names (e.g. most of the macros in
object.h).

Now that we have explicitly tagged the struct and typedef doc
comments in memory.h and object.h, we don't need that hack
anymore.  This will make the documentation for the macros in
object.h finally be rendered as expected.

Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20201003024123.193840-6-ehabkost@redhat.com>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>