MIPS: Fix build error for crash_dump.c in 3.10-rc1

MIPS: Fix build error for crash_dump.c in 3.10-rc1

This patch fixes crash_dump.c build error. Build error logs are as follow.

arch/mips/kernel/crash_dump.c: In function 'kdump_buf_page_init':
arch/mips/kernel/crash_dump.c:67: error: implicit declaration of function 'kmalloc'
arch/mips/kernel/crash_dump.c:67: error: assignment makes pointer from integer without a cast

Signed-off-by: EunBong Song <eunb.song@samsung.com>
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/5238/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>