ext4: rename ext4_claim_free_blocks() to ext4_claim_free_clusters()

This function really claims a number of free clusters, not blocks, so
rename it so it's clearer what's going on.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

diff --cc fs/ext4/balloc.c
Simple merge

diff --cc fs/ext4/ext4.h
Simple merge

diff --cc fs/ext4/inode.c
Simple merge

diff --cc fs/ext4/mballoc.c
Simple merge