Btrfs: fix number of transaction units required to create symlink

Btrfs: fix number of transaction units required to create symlink

Orabug: 23331027

[ Upstream commit 9269d12b2d57d9e3d13036bb750762d1110d425c ]

We weren't accounting for the insertion of an inline extent item for the
symlink inode nor that we need to update the parent inode item (through
the call to btrfs_add_nondir()). So fix this by including two more
transaction units.

Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
(cherry picked from commit a1f535acffbd95ae6ae81656e8bba39af094c3f0)

Signed-off-by: Dan Duval <dan.duval@oracle.com>