x86/paravirt: clean up typos and grammaros

Drive-by clean up of the comment.

[ Impact: cleanup]

Signed-off-by: Bill Wendling <morbo@google.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20220902213750.1124421-2-morbo@google.com