Switches calls to syscall to x/sys, which is more up to date.
This is fixes a number of possible bugs on other architectures
where ioctl tcget and tcset aren't implemented correctly.
There are a few remaining syscall references, because x/sys doesn't
have an Errno implementation yet.
Also removes a ppc64le and cgo build tag that fixes building on
ppc64le without cgo
Signed-off-by: Christopher Jones <tophj@linux.vnet.ibm.com>
