When boot complete, write fs_ready 1 to notify cnss2.
Note fs_ready must not be written too early, otherwise
it will not download firmware successfully.
Bug: 202809487
Test: Build pass
Change-Id: I990257d168550e512ae94287ca79095201b16e2b
based on panther 0e0ae4dd4045e00dd50826d5c411351d47949d92
No-Typo-Check: based on above commit
Bug: 202250383
Change-Id: I7dbcba9fc0644cf8e547c59b14a544701adc484b