move time64 ioctl numbers to generic bits/ioctl.h

move time64 ioctl numbers to generic bits/ioctl.h

now that all 32-bit archs have 64-bit time types, the values for the
time-related ioctls can be shared. the mechanism for this is an
arch/generic version of the bits header. archs which don't use the
generic header still need to duplicate the definitions.

x32, which does not use the new time64 values of the macros, already
has its own overrides, so this commit does not affect it.