MIPS: Fix GCC-4.6 'set but not used' warning in arch/mips/mm/init.c
MIPS: Fix GCC-4.6 'set but not used' warning in arch/mips/mm/init.c

Under some combinations of CONFIG_*, lastpfn in page_is_ram is 'set
but not used'.  Mark it as __maybe_unused to quiet the warning/error.

Signed-off-by: David Daney <0662de36cfb0706ed279bff52abef14720945acc@caviumnetworks.com>
To: 562397917b9a8bf316569a848858b12fb417723f@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/2033/
Signed-off-by: Ralf Baechle <92f48d309cda194c8eda36aa8f9ae28c488fa208@linux-mips.org>

TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs