befs: fix comment style

The description of befs_load_sb was confusing the kernel-doc system since,
because it starts with /**, it thinks it will document the function with
kernel-doc formatting. Which it isn't.

Fix other comment style issues in the file while we are at it.

Signed-off-by: Luis de Bethencourt <luisbg@osg.samsung.com>
Signed-off-by: Salah Triki <salah.triki@gmail.com>