commonlib: Add assembly optimization for ipchksum() on x86

This patch adds a bit of optimized assembly code to the ipchksum()
algorithm for x86 targets in order to take advantage of larger load
sizes and the add-with-carry instruction. The same assembly (with one
minor manual tweak) works for both 32 and 64 bit mode (with most of the
work being done by GCC which automatically inserts `rax` or `eax` in the
inline assembly depending on the build target).

Change-Id: I484620dc14679ff5ca02b2ced2f84650730a6efc
Signed-off-by: Julius Werner <jwerner@chromium.org>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/80255
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

0 files changed, 0 insertions, 0 deletions