x86/coco/sev: Convert has_cpuflag() to use cpu_feature_enabled()
Drop one redundant definition, while at it.
There should be no functional changes.
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://patch.msgid.link/20251031122122.GKaQSpwhLvkinKKbjG@fat_crate.local