smm: Switch from %edx to %ebx

%edx gets clobbered before the c handler is invoked. This is just a
cleanup cl to make the next cl look clean.

BUG=b:80539294
TEST=verified SMI still works on grunt.

Change-Id: I21bf41ed4fdeaaa8737c883f202a39cb57c2b517
Signed-off-by: Raul E Rangel <rrangel@chromium.org>
Reviewed-on: https://review.coreboot.org/27228
Reviewed-by: Martin Roth <martinroth@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
1 file changed