KVM: SPDX style and spelling fixes

SPDX comments use use /* */ style comments in headers anad
// style comments in .c files.  Also fix two spelling mistakes.

Signed-off-by: Tom Rix <trix@redhat.com>
Message-Id: <20220410153840.55506-1-trix@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>