parisc: Increase thread and stack size to 32kb

Since kernel 4.11 the thread and irq stacks on parisc randomly overflow
the default size of 16k. The reason why stack usage suddenly grew is yet
unknown.

Signed-off-by: Helge Deller <deller@gmx.de>
Cc: stable@vger.kernel.org # 4.11+
Signed-off-by: Helge Deller <deller@gmx.de>