y2038: ia64: Remove unneeded ipc uapi header files

The ia64 ipcbuf/msgbuf/sembuf/shmbuf header files are all identical
to the version from asm-generic.

This patch removes the files and replaces them with 'generic-y'
statements as part of the y2038 changes. While ia64 no longer has
a compat mode and doesn't need the file any more, it seem nicer
to clean this up anyway.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>