x86-32: Make AT_VECTOR_SIZE_ARCH=2

Both x86-32 and x86-64 with 32-bit compat use ARCH_DLINFO_IA32,
which defines two saved_auxv entries.  But system.h only defines
AT_VECTOR_SIZE_ARCH as 2 for CONFIG_IA32_EMULATION, not for
CONFIG_X86_32.  Fix that.

Signed-off-by: Serge E. Hallyn <serue@us.ibm.com>
LKML-Reference: <20100209023502.GA15408@us.ibm.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>