parisc: Fix exported address of os_hpmc handler

In the C-code we need to put the physical address of the hpmc handler in
the interrupt vector table (IVA) in order to get HPMCs working.  Since
on parisc64 function pointers are indirect (in fact they are function
descriptors) we instead export the address as variable and not as
function.

This reverts a small part of commit f39cce65 ("parisc: Add
cfi_startproc and cfi_endproc to assembly code").

Signed-off-by: Helge Deller <deller@gmx.de>
Cc: <stable@vger.kernel.org>    [4.9+]