The latest GKI has added a vendor hook to tune ra size in do_sync_mmap_readahead(). Add a new handler to limit the mmap readahead size. Change-Id: I609fd3e4583b37561faea5e108ca9e664f956098 Reviewed-on: https://gerrit.mot.com/2676241 SME-Granted: SME Approvals Granted SLTApproved: Slta Waiver Tested-by: Jira Key Reviewed-by: Zonghua Liu <a17671@motorola.com> Reviewed-by: Huosheng Liao <liaohs@motorola.com> Reviewed-by: Chuanchun Zhu <zhucc2@motorola.com> Submit-Approved: Jira Key Reviewed-on: https://gerrit.mot.com/2676239