xfs: move two more RT specific functions into CONFIG_XFS_RT

The last cleanup introduced two harmless warnings:

fs/xfs/xfs_fsmap.c:480:1: warning: '__xfs_getfsmap_rtdev' defined but not used
fs/xfs/xfs_fsmap.c:372:1: warning: 'xfs_getfsmap_rtdev_rtbitmap_helper' defined but not used

This moves those two functions as well.

Fixes: bb9c2e54

 ("xfs: move more RT specific code under CONFIG_XFS_RT")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>