x86/signal: Merge get_sigframe()

Adapt the native get_sigframe() function so that the compat signal code
can use it.

Signed-off-by: Brian Gerst <brgerst@gmail.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>
Link: https://lore.kernel.org/r/20220606203802.158958-6-brgerst@gmail.com


Signed-off-by: Borislav Petkov <bp@suse.de>