tile: use si_int instead of si_ptr for compat_siginfo

To be compatible with the generic get_compat_sigevent(), the
copy_siginfo_to_user32() and thus copy_siginfo_from_user32()
have to use si_int instead of si_ptr.  Using si_ptr means that
for the case of ILP32 compat code running in big-endian mode,
we would end up copying the high 32 bits of the pointer value
into si_int instead of the desired low 32 bits.

Signed-off-by: Chris Metcalf <cmetcalf@ezchip.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>