befs: befs: fix style issues in datastream.c

Fixing the following checkpatch.pl errors:

ERROR: "foo * bar" should be "foo *bar"
+                            befs_blocknr_t blockno, befs_block_run * run);

WARNING: Missing a blank line after declarations
+       struct buffer_head *bh;
+       befs_debug(sb, "---> %s length: %llu", __func__, len);

WARNING: Block comments use * on subsequent lines
+       /*
+          Double indir block, plus all the indirect blocks it maps.

(and other instances of these)

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