ext4: fix symbolic enum printing in trace output

ext4: fix symbolic enum printing in trace output

Trace's macro __print_flags() produce raw event's decraration w/o knowing actual
flags value

cat /sys/kernel/debug/tracing/events/ext4/ext4_ext_map_blocks_exit/format
..
__print_flags(REC->mflags, "", { (1 << BH_New),

For that reason we have to explicitly define it via special macro TRACE_DEFINE_ENUM()
Also add missed EXTENT_STATUS_REFERENCED flag.

#Before patch
ext4:ext4_ext_map_blocks_exit: dev 253,0 ino 2 flags  lblk 0 pblk 4177 len 1 mflags 0x20 ret 1
ext4:ext4_ext_map_blocks_exit: dev 253,0 ino 12 flags CREATE lblk 0 pblk 34304 len 1 mflags 0x60 ret 1

#With patch
ext4:ext4_ext_map_blocks_exit: dev 253,0 ino 2 flags  lblk 0 pblk 4177 len 1 mflags M ret 1
ext4:ext4_ext_map_blocks_exit: dev 253,0 ino 12 flags CREATE lblk 0 pblk 34816 len 1 mflags NM ret 1

Signed-off-by: Dmitry Monakhov <dmonakhov@gmail.com>
Link: https://lore.kernel.org/r/20191114200147.1073-1-dmonakhov@gmail.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>