staging: android: ashmem: lseek failed due to no FMODE_LSEEK.

vfs_llseek will check whether the file mode has
FMODE_LSEEK, no return failure. But ashmem can be
lseek, so add FMODE_LSEEK to ashmem file.

Change-Id: Ia78ef4c7c96adb89d52e70b63f7c00636fe60d01
Signed-off-by: zhangshuxiao <zhangshuxiao@xiaomi.com>
(cherry picked from commit 6c8d409129bbebe36cde9f8e511011756216163a)
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>