Update aarch64 bits/hwcap.h, dl-procinfo.c for Linux 4.16 HWCAP_ASIMDFHM.

This patch updates the aarch64 bits/hwcap.h and dl-procinfo.c for the
new HWCAP_ASIMDFHM value in Linux 4.16.

Tested with build-many-glibcs.py for aarch64-linux-gnu.

	* sysdeps/unix/sysv/linux/aarch64/bits/hwcap.h (HWCAP_ASIMDFHM):
	New macro.
	* sysdeps/unix/sysv/linux/aarch64/dl-procinfo.c (_DL_HWCAP_COUNT):
	Increase to 24.
	(_dl_aarch64_cap_flags): Add asimdfhm.