S390: Mark vx and vxe as important hwcap.

This patch adds vx and vxe as important hwcaps
which allows one to provide shared libraries
tuned for platforms with non-vx/-vxe, vx or vxe.

ChangeLog:

	* sysdeps/s390/dl-procinfo.h (HWCAP_IMPORTANT):
	Add HWCAP_S390_VX and HWCAP_S390_VXE.

(cherry picked from commit 61f5e947)

Conflicts:
	ChangeLog