parisc: Use natural CPU alignment for bug_table

Make sure that the __bug_table section gets 32- or 64-bit aligned,
depending if a 32- or 64-bit kernel is being built.
Mark it non-writeable and use .blockz instead of the .org assembler
directive to pad the struct.

Signed-off-by: Helge Deller <deller@gmx.de>
Cc: stable@vger.kernel.org   # v6.0+