xfs: Fix undefined behavior of shift into sign bit

With gcc-5:

    In file included from ./include/trace/define_trace.h:102:0,
		     from ./fs/xfs/scrub/trace.h:988,
		     from fs/xfs/scrub/trace.c:40:
    ./fs/xfs/./scrub/trace.h: In function ‘trace_raw_output_xchk_fsgate_class’:
    ./fs/xfs/scrub/scrub.h:111:28: error: initializer element is not constant
     #define XREP_ALREADY_FIXED (1 << 31) /* checking our repair work */
				^

Shifting the (signed) value 1 into the sign bit is undefined behavior.

Fix this for all definitions in the file by shifting "1U" instead of
"1".

This was exposed by the first user added in commit 466c525d
("xfs: minimize overhead of drain wakeups by using jump labels").

Fixes: 160b5a78 ("xfs: hoist the already_fixed variable to the scrub context")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Dave Chinner <david@fromorbit.com>