Revert unintentional "volatile" changes in ipc/msg.c

Commit 5a06a363 ("[PATCH] ipc/msg.c:
clean up coding style") breaks fakeroot on Alpha (variously hangs or
oopses), according to a report by Falk Hueffner.

The fact that the code seems to rely on compiler access ordering through
the use of "volatile" is a pretty certain sign that the code has locking
problems, and we should fix those properly and then remove the whole
"volatile" entirely.

But in the meantime, the movement of "volatile" was unintentional, and
should be reverted.

Cc: Falk Hueffner <falk@debian.org>
Cc: Andrew Morton <akpm@osdl.org>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>