objtool: Optimize layout of struct special_alt

Reduce the size of struct special_alt from 72 to 64 bytes.

Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Link: https://lore.kernel.org/r/20221216-objtool-memory-v2-7-17968f85a464@weissschuh.net


Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>