efi, pstore: Cocci spatch "memdup.spatch"

Change a kmalloc() + memcpy() pair for a single kmemdup() call.

Signed-off-by: Thomas Meyer <thomas@m3y3r.de>
Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Tony Luck <tony.luck@intel.com>