ieee1394: sbp2: update includes

Remove unused includes.  Add missing includes, i.e. explicitly include
all used headers.  Sort includes alphabetically.  Replace one call to
signal_pending(current) to avoid to include headers just for this line.

Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>

diff --cc drivers/ieee1394/sbp2.c
Simple merge