x86: Fix uv bau sending buffer initialization

x86: Fix uv bau sending buffer initialization

commit 9c26f52b900f7207135bafc8789e1a4f5d43e096 upstream.

The initialization of the UV Broadcast Assist Unit's sending
buffers was making an invalid assumption about the
initialization of an MMR that defines its address.

The BIOS will not be providing that MMR.  So
uv_activation_descriptor_init() should unconditionally set it.

Tested on UV simulator.

Signed-off-by: Cliff Wickman <cpw@sgi.com>
LKML-Reference: <E1MJTfj-0005i1-W8@eag09.americas.sgi.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>