Make cpuid functions usable when compiled with PIC

This avoids using EBX and instead uses EDI where possible,
and ESI when necessary to get the EBX value out.

This allows me to enable -fpic for SMM TSEG code.

Also add a new CPUID extended function to query with ECX set.

Change-Id: I10dbded3f3ad98a39ba7b53da59af6ca3145e2e5
Signed-off-by: Duncan Laurie <dlaurie@google.com>
Reviewed-on: http://review.coreboot.org/764
Tested-by: build bot (Jenkins)
Reviewed-by: Mathias Krause <minipli@googlemail.com>