LU-15544 osd: Handle removal of EXT4_GET_BLOCKS_KEEP_SIZE

LU-15544 osd: Handle removal of EXT4_GET_BLOCKS_KEEP_SIZE

Linux commit v5.6-rc4-4-g4337ecd1fe99
  ext4: remove EXT4_EOFBLOCKS_FL and associated code

This change removes the define for EXT4_EOFBLOCKS_FL
as well as the enum value EXT_INODE_EOFBLOCKS.

Linux commit v5.7-rc4-4-g9e52484c7133
  ext4: remove EXT4_GET_BLOCKS_KEEP_SIZE flag

This change removes the define for EXT4_GET_BLOCKS_KEEP_SIZE

Fix the usage in osd_io.c to check for the existence of the
related definitions and remove the configure test.

Test-Parameters: trivial
Fixes: 791f656a03 ("LU-14776 ldiskfs: Add Ubuntu 20.04 HWE support")
HPE-bug-id: LUS-10744
Signed-off-by: Shaun Tancheff <shaun.tancheff@hpe.com>
Change-Id: I883708ce2879f4d7d41ad3f7b75db2e751f6eb9b
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/49134
Reviewed-by: Neil Brown <neilb@suse.de>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>