parisc: Reduce size of the bug_table on 64-bit kernel by half

Enable GENERIC_BUG_RELATIVE_POINTERS which will store 32-bit relative
offsets to the bug address and the source file name instead of 64-bit
absolute addresses. This effectively reduces the size of the
bug_table[] array by half on 64-bit kernels.

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