Remove __ASSUME_F_GETOWN_EX.
This patch removes __ASSUME_F_GETOWN_EX now it can be assumed to be
true unconditionally.
Tested x86_64 that disassembly of installed shared libraries is
unchanged by this patch.
* sysdeps/unix/sysv/linux/kernel-features.h
(__ASSUME_F_GETOWN_EX): Remove macro.
* sysdeps/unix/sysv/linux/fcntl.c: Do not include
<kernel-features.h>.
(miss_F_GETOWN_EX): Remove variable or macro.
(do_fcntl): Do not check miss_F_GETOWN_EX.
(do_fcntl) [!__ASSUME_F_GETOWN_EX]: Remove conditional code.