MIPS: 64-bit: Fix build if !CONFIG_MODULES

MIPS: 64-bit: Fix build if !CONFIG_MODULES

Fix build failure if building a monolithic kernel due to
arch/mips/kernel/Kconfig selecting MODULES_USE_ELF_REL[A] without checking
to see if MODULES is set or not.  This leads to 'struct module' not
existing, which triggers a compile failure in arch/mips/kernel/module-rela.c
when the compiler attempts to dereference me->name:

  CC      arch/mips/kernel/module-rela.o
arch/mips/kernel/module-rela.c: In function ‘apply_r_mips_26_rela’:
arch/mips/kernel/module-rela.c:38:74: error: dereferencing pointer to incomplete type
arch/mips/kernel/module-rela.c:46:12: error: dereferencing pointer to incomplete type
arch/mips/kernel/module-rela.c: In function ‘apply_relocate_add’:
arch/mips/kernel/module-rela.c:133:13: error: dereferencing pointer to incomplete type
make[2]: *** [arch/mips/kernel/module-rela.o] Error 1

Signed-off-by: Joshua Kinard <kumba@gentoo.org>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/4749/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>