proc/vmcore: Fix i386 build error of missing copy_oldmem_page_encrypted()

Lianbo reported a build error with a particular 32-bit config, see Link
below for details.

Provide a weak copy_oldmem_page_encrypted() function which architectures
can override, in the same manner other functionality in that file is
supplied.

Reported-by: Lianbo Jiang <lijiang@redhat.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
CC: x86@kernel.org
Link: http://lkml.kernel.org/r/710b9d95-2f70-eadf-c4a1-c3dc80ee4ebb@redhat.com

fs/proc/vmcore.c

@@ -187,6 +187,16 @@ int __weak remap_oldmem_pfn_range(struct vm_area_struct *vma,
 	return remap_pfn_range(vma, from, pfn, size, prot);
 }
 
+/*
+ * Architectures which support memory encryption override this.
+ */
+ssize_t __weak
+copy_oldmem_page_encrypted(unsigned long pfn, char *buf, size_t csize,
+			   unsigned long offset, int userbuf)
+{
+	return copy_oldmem_page(pfn, buf, csize, offset, userbuf);
+}
+
 /*
  * Copy to either kernel or user space
  */