x86, uv: uv_global_gru_mmr_address() macro fix

Fix bug in uv_global_gru_mmr_address macro.  Macro failed
to cast an int value to a long prior to a left shift > 32.

Signed-off-by: Jack Steiner <steiner@sgi.com>
LKML-Reference: <20100107161240.GA2610@sgi.com>
Cc: <stable@kernel.org>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>