btrfs-progs: docs: fix formatting of btrfs(5)

Two paragraphs for 'discard' mount option were not aligned in the
section and the swapfile bullet list was squashed to one line. All in
the manual page output.

Signed-off-by: David Sterba <dsterba@suse.com>

Documentation/btrfs-man5.asciidoc

@@ -217,14 +217,14 @@ support discard for it to work. if the backing device does not support
 asynchronous queued TRIM, then this operation can severely degrade performance,
 because a synchronous TRIM operation will be attempted instead. Queued TRIM
 requires newer than SATA revision 3.1 chipsets and devices.
-
++
 If it is not necessary to immediately discard freed blocks, then the `fstrim`
 tool can be used to discard all free blocks in a batch. Scheduling a TRIM
 during a period of low system activity will prevent latent interference with
 the performance of other operations. Also, a device may ignore the TRIM command
 if the range is too small, so running a batch discard has a greater probability
 of actually discarding the blocks.
-
++
 If discarding is not necessary to be done at the block freeing time, there's
 `fstrim`(8) tool that lets the filesystem discard all free blocks in a batch,
 possibly not much interfering with other operations. Also, the device may
@@ -639,31 +639,32 @@ SWAPFILE SUPPORT
 The swapfile is supported since kernel 5.0. Use `swapon`(8) to activate the
 swapfile. There are some limitations of the implementation in btrfs and linux
 swap subystem:
-+
+ 
 * filesystem - must be only single device
 * swapfile - the containing subvolume cannot be snapshotted
 * swapfile - must be preallocated
 * swapfile - must be nodatacow (ie. also nodatasum)
 * swapfile - must not be compressed
-+
+ 
 The limitations come namely from the COW-based design and mapping layer of
 blocks that allows the advanced features like relocation and multi-device
 filesystems. However, the swap subsystem expects simpler mapping and no
 background changes of the file blocks once they've been attached to swap.
-+
+ 
 With active swapfiles, the following whole-filesystem operations will skip
 swapfile extents or may fail:
+ 
 * balance - block groups with swapfile extents are skipped and reported, the rest will be processed normally
 * resize grow - unaffected
 * resize shrink - works as long as the extents are outside of the shrunk range
 * device add - a new device does not interfere with existing swapfile and this operation will work, though no new swapfile can be activated afterwards
 * device delete - if the device has been added as above, it can be also deleted
 * device replace - dtto
-+
+ 
 When there are no active swapfiles and a whole-filesystem exclusive operation
 is running (ie. balance, device delete, shrink), the swapfiles cannot be
 temporarily activated. The operation must finish first.
-+
+ 
 --------------------
 # truncate -s 0 swapfile
 # chattr +C swapfile