[GFS2] Add consts to various bits of rgrp.c
[GFS2] Add consts to various bits of rgrp.c

There are a couple of routines which scan bitmaps where we can
mark the bitmaps const, plus a couple of call sites that can
be updated too.

Signed-off-by: Steven Whitehouse <9801c4ef11586b619a1c43ac9377eea2aee672dd@redhat.com>

KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs