parisc: Use generic init_task

Same code, except: The alignment of init_thread_union is handled via
the linker script, so no point to have it with the data structure. The
extra asm(".data") looks like a leftover from an asm to C conversion
and is pointless.

Use the generic version.

Move the page table data to parisc/mm/init.c and get rid of
parisc/../init_task.c

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: James E.J. Bottomley <jejb@parisc-linux.org>
Link: http://lkml.kernel.org/r/20120503085035.150896946@linutronix.de