core: squashed commit of:

Initial bringup system-core

Qcril : Added diag permission to Ril

diag: Remove world read/write permissions from /dev/diag

/dev/diag has world read/write permissions which is considered
a security risk.  Remove these permissions.  Add new qcom_diag
group for access to /dev/diag

CRs-Fixed: 356415

Change-Id: I41c950d9b24742b25c4eada63d62d493550c384d