x86/sev: Use "SEV: " prefix for messages from sev.c

The source file has been renamed froms sev-es.c to sev.c, but the
messages are still prefixed with "SEV-ES: ". Change that to "SEV: " to
make it consistent.

Fixes: e759959f ("x86/sev-es: Rename sev-es.{ch} to sev.{ch}")
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210622144825.27588-4-joro@8bytes.org