xfs: Fix the return value of xfs_rtcopy_summary()

xfs: Fix the return value of xfs_rtcopy_summary()

xfs_rtcopy_summary() should return the appropriate error code
instead of always returning 0. The caller of this function which is
xfs_growfs_rt_bmblock() is already handling the error.

Fixes: e94b53ff699c ("xfs: cache last bitmap block in realtime allocator")
Signed-off-by: Nirjhar Roy (IBM) <nirjhar.roy.lists@gmail.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: stable@vger.kernel.org # v6.7
Signed-off-by: Carlos Maiolino <cem@kernel.org>