m68k: Fix task info flags handling for 68000

m68k: Fix task info flags handling for 68000

The logic for deciding what to do after a syscall should be checking
if any of the lower byte bits are set and then checking if the reschedule
bit is set.

Currently we are loading the top word, checking if any bits are set
(which never seems to be true) and thus jumping over loading the
whole long and checking if the reschedule bit is set.

We get the thread info in two places so split that logic out in
a macro and then fix the code so that it loads the byte of the flags
we need to check, checks if anything is set and then checks if
the reschedule bit in particular is set.

Reported-by: Christoph Plattner <christoph.plattner@gmx.at>
Signed-off-by: Daniel Palmer <daniel@0x0f.com>
Signed-off-by: Greg Ungerer <gerg@kernel.org>