Revert "mm: Set VM_MAX_READAHEAD to 1024 as default"

This reverts commit c65615d87fb6f3037b89aca5946e2db2c2524ad4.
Revert "Revert "mm: Set VM_MAX_READAHEAD to 1024 as default""

This reverts commit 37a74b6d9b8090351009eb5e0d2794b1bab271a5.
Fix build from frame size warning