y2038: arm64: Extend sysvipc compat data structures

Both 32-bit amd 64-bit ARM use the asm-generic header files for their
sysvipc data structures, so no special care is needed to make those
work beyond y2038, with the one exception of compat mode: Since there
is no asm-generic definition of the compat mode IPC structures, ARM64
provides its own copy, and we make those match the changes in the native
asm-generic header files.

There is sufficient padding in these data structures to extend all
timestamps to 64 bit, but on big-endian ARM kernels, the padding
is in the wrong place, so the C library has to ensure it reassembles
a 64-bit time_t correctly.

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