runtime: fix assembly syntax

Some assembler doesn't accept ULL suffix. In fact the suffix
is not really necessary. Drop it.

Change-Id: Ib64b2b566def0ebf47c7959b8423b08ae5fbbe52
Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/180217
Reviewed-by: Ian Lance Taylor <iant@golang.org>