[coreboot-gerrit] Patch merged into coreboot/master: libpayload: x86/exec - simplify and robustify the code

the following patch was just integrated into master:
commit 57dc93c967f45167f09e7817266ebb4f3dbda62a
Author: Mathias Krause 
Date:   Sat Feb 11 21:02:08 2017 +0100

libpayload: x86/exec - simplify and robustify the code

Simplify the code by directly using the arguments on the stack as base
    pointer relative memory references, instead of loading them into
    intermediate registers first.

Make it more robust by preserving all callee saved registers mandated by
    the C calling convention (and only those), namely EBP, EBX, ESI and EDI.

Don't assume anything about the register state when the called function
    returns -- beside the segment registers and the stack pointer to be
    still the same as before the call.

Change-Id: I383d6ccefc5b3d5cca37a1c9b638c231bbc48aa8
    Signed-off-by: Mathias Krause 
    Reviewed-on: https://review.coreboot.org/18335
    Reviewed-by: Aaron Durbin 
    Tested-by: build bot (Jenkins)

See https://review.coreboot.org/18335 for details.

-gerrit