x86 VSDO: Fix Kconfig help

COMPAT_VDSO has 2 help text blocks, but kconfig only uses the
last one found, so merge the 2 blocks.

It would be real nice if kconfig would warn about this.

Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
LKML-Reference: <4AF9FB6C.70003@oracle.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>