MIPS: SNI: pcit: Fix build error with CONFIG_PCI=n disabled.

  CC      arch/mips/sni/pcit.o
arch/mips/sni/pcit.c:150:30: warning: ‘sni_pcit_controller’ defined but not used [-Wunused-variable]

Signed-off-by: Ralf Baechle <ralf@linux-mips.org>