[GFS2] Move part of gfs2_block_map into a separate function
[GFS2] Move part of gfs2_block_map into a separate function

This is required to enable future changes to the block
mapping code.

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

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