m68knommu: fix use of un-defined _TIF_WORK_MASK

The _TIF_WORK_MASK definition was removed in the clean up of MMU and
non-MMU arch/m68k/include/asm/thread_info*.h files (this was commit
cddafa35, "merge MMU and non-MMU
thread_info.h").

It didn't get cleaned out of the entry.S code for the 68328 and 68360
based platforms. And it was replaced by a hard coded constant mask for
coldfire platforms. There is currently no need to mask any of these bits,
so fix all uses (and former uses) to check for any non-zero value.

Signed-off-by: Greg Ungerer <gerg@uclinux.org>