FRV: Fix const sections change

Add __pminitconst to fix the build, otherwise the following error can occur:

  arch/frv/kernel/setup.c:187:47: error: expected '=', ',', ';', 'asm' or '__attribute__' before '*' token
  arch/frv/kernel/setup.c:386:2: error: 'clock_cmodes' undeclared (first use in this function)
  arch/frv/kernel/setup.c:571:6: error: 'clock_cmodes' undeclared (first use in this function)
  make[2]: *** [arch/frv/kernel/setup.o] Error 1

http://kisskb.ellerman.id.au/kisskb/buildresult/7344691/

Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>