staging: android: ashmem: add missing include

Include <linux/types.h> into ashmem.h to ensure referenced types are defined

Signed-off-by: Rom Lemarchand <romlem@android.com>
Change-Id: Iac18ed86dd47296d02a269607b1514724aaa9958
(cherry picked from commit 0d7c7ba9f6428e694130a40e270516618f27ce14)