stddef.h: fix zeroptr's definition

As Aaron pointed out, the old definition made the compiler emit two
memory accesses, to 0 (for derefencing) and then reading at whatever
address could be read from there.

Change-Id: I5cdd53f5bd2d2397c43f09f3e5fa46be08744b01
Found-by: Aaron Durbin <adurbin@chromium.org>
Signed-off-by: Patrick Georgi <pgeorgi@chromium.org>
Reviewed-on: https://review.coreboot.org/14342
Tested-by: build bot (Jenkins)
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
1 file changed