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>

arch/mips/kernel/crash_dump.c

@@ -2,6 +2,7 @@
 #include <linux/bootmem.h>
 #include <linux/crash_dump.h>
 #include <asm/uaccess.h>
+#include <linux/slab.h>
 
 static int __init parse_savemaxmem(char *p)
 {