parisc: fix module loading failure of large kernel modules

On 32bit (and sometimes 64bit) and with big kernel modules like xfs or
ipv6 the relocation types R_PARISC_PCREL17F and R_PARISC_PCREL22F may
fail to reach their PLT stub if we only create one big stub array for
all sections at the beginning of the core or init section.

With this patch we now instead add individual PLT stub entries
directly in front of the code sections where the stubs are actually
called. This reduces the distance between the PCREL location and the
stub entry so that the relocations can be fulfilled.

While calculating the final layout of the kernel module in memory, the
kernel module loader calls arch_mod_section_prepend() to request the
to be reserved amount of memory in front of each individual section.

Tested with 32- and 64bit kernels.

Signed-off-by: Helge Deller <deller@gmx.de>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>