Fix Linux fallocate tests for EOPNOTSUPP

The fallocate syscall might fail on Linux due missing support from
underlying filesystem (for instance some NFS versions).  This patch
adds this check for fallocate tests.  It also moves tst-fallocate{64}
to 'io' folder (since it is on fallocate{64} is built).

Checked on x86_64.

	* sysdeps/unix/sysv/linux/Makefile [$(subdir) = math] (tests): Move
	tst-fallocate{64}.
	* sysdeps/unix/sysv/linux/tst-fallocate-common.c: Check for EOPNOTSUPP
	on syscall return.