ANDROID: Incremental fs: Fix sparse errors

Fix all sparse errors in fs/incfs except
fs/incfs/integrity.c:192:9: warning: Variable length array is used

Test: incfs_test passes
Bug: 133435829
Change-Id: I9c2e26e4e1a06a894977f11a3c8559b968dd115e
Signed-off-by: Paul Lawrence <paullawrence@google.com>