[ALPS03868216] wlan_assistant: allow to write nvram to driver

Wlan driver has no permission to read nvram and wifi.cfg, wifi_fw.cfg,
so need to read that in wlan_assistant, and then write it to wlan
driver

MTK-Commit-Id: 1df286414a6fefe023069318bd4e7f14606d9fe1

Change-Id: I5e8adcfeb17b043fedec5bd2d65b25fc58f59bae
CR-Id: ALPS03868216
Feature: [Module]Wi-Fi HAL