x86: ia32.h: remove unused struct sigfram32 and rt_sigframe32
Impact: cleanup
Remove struct sigfram32 and rt_sigframe32 because there is no user.
Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>