keymaster: Change shared library path

Change shared library path from /system/lib to /vendor/lib.

Change-Id: I8a1a314953aaf674e22f7fbcf63012e86aad9d76
keymaster: Fix compiler warnings

Fixes the compiler warnings by modifying the function definition.

Change-Id: Ia3c75f75cdb7434379d7601027d804edc2b8eebf
keymaster: Add support for loading keymaste image

If keymaster image is not found in vendor/* look for
keymaste image file in firmware/image.

Change-Id: I8c5df5c585e23c2387a6f4eb94d968532b397eed