linux(4): Convert flags in timerfd_create
The timerfd is introduced in FreeBSD 14, and the Linux ABI timerfd is
also moved to FreeBSD native timerfd, but it can't work well as Linux
TFD_CLOEXEC and TFD_NONBLOCK haven't been converted to FreeBSD
TFD_CLOEXEC and TFD_NONBLOCK.
Reviewed by: dchagin, jfree
Differential revision: https://reviews.freebsd.org/D41708
MFC after: 1 week