checksyscalls: fix up mq_timedreceive and stat exceptions

mq_timedreceive was spelled incorrectly, and we need exceptions
for new architectures that leave out newstat or stat64, implementing
only statx() now.

Fixes: 48166e6e ("y2038: add 64-bit time_t syscalls to all 32-bit architectures")
Fixes: bf4b6a7d ("y2038: Remove stat64 family from default syscall set")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>