goldfish_pipe.c

- first_page and last_page are page start addresses, so the type
  has to be long for x64

- as those variables are addresses, their difference doesn't
  give the number of pages.

Signed-off-by: Yurii Zubrytskyi <zyy@google.com>
Change-Id: Ia00420c3261dea0ca4bba1f72125a1641c503000