KVM: SVM: Check for an unexpected VM-Exit after RETPOLINE "fast" handling

KVM: SVM: Check for an unexpected VM-Exit after RETPOLINE "fast" handling

Check for an unexpected/unhandled VM-Exit after the manual RETPOLINE=y
handling.  The entire point of the RETPOLINE checks is to optimize for
common VM-Exits, i.e. checking for the rare case of an unsupported
VM-Exit is counter-productive.  This also aligns SVM and VMX exit handling.

No functional change intended.

Reviewed-by: Yosry Ahmed <yosry.ahmed@linux.dev>
Link: https://patch.msgid.link/20251230211347.4099600-4-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>