powerpc: Update AT_HWCAP[2] bits

Linux commit ID a4700a26107241cc7b9ac8528b2c6714ff99983d reserved 2 more
bits for the instructions darn (Deliver a Random Number) and scv (System
Call Vectored).

Linux commit ID 6997e57d693b07289694239e52a10d2f02c3a46f reserved
another bit for internal usage.

	* sysdeps/powerpc/bits/hwcap.h: Add PPC_FEATURE2_DARN and
	PPC_FEATURE2_SCV.
	* sysdeps/powerpc/dl-procinfo.c (_dl_powerpc_cap_flags): Add scv
	and darn.