libpayload: Add ptrdiff_t typedef

vboot2 in payloads (eg depthcharge) needs it.

Change-Id: I4e79ae29cc282c8680f21686befd35c4ff461b3a
Signed-off-by: Patrick Georgi <pgeorgi@google.com>
Reviewed-on: http://review.coreboot.org/11922
Tested-by: build bot (Jenkins)
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-by: Nico Huber <nico.h@gmx.de>
1 file changed