ext4: translate a few more map flags to strings in tracepoints

ext4: translate a few more map flags to strings in tracepoints

As new ext4_map_blocks() flags have been added, not all have gotten flag
bit to string translations to make tracepoint output more readable.
Fix that, and go one step further by adding a translation for the
EXT4_EX_NOCACHE flag as well.  The EXT4_EX_FORCE_CACHE flag can never
be set in a tracepoint in the current code, so there's no need to
bother with a translation for it right now.

Signed-off-by: Eric Whitney <enwlinux@gmail.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20200415203140.30349-3-enwlinux@gmail.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>