parisc: Use _TIF_USER_WORK_MASK in entry.S

The constant _TIF_USER_WORK_MASK will get extended by additional flags
in the future, so check against the bits set in this mask - with the
exception of _TIF_NEED_RESCHED which was tested a few lines above.

Signed-off-by: Helge Deller <deller@gmx.de>