Fix refcount leaks in the SGX Linux compat ioctl handler.

Some argument validation error paths would return without releasing the
file reference obtained at the beginning of the function.

While here, fix some style bugs and remove trivial debug prints.

Reviewed by: kib
MFC after: 1 week
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D19214