ANDROID: firmware_loader: Restore permissions for firmware class path

Permissions for accessing firmware class path was wrongly set to write only for root
as a result the path can not be read. Restore permissions, so that it can be read.
Add a getter function to read the class path.

Bug: 240542962
Fixes: d551647f ("ANDROID: firmware_loader: Add support for customer firmware paths")
Fixes: 87abd99c ("ANDROID: firmware_loader: Fix warning with firmware_param_path_set").
Change-Id: I65f434db6a0c31d0b01a5a58cfba0d241e98dd0e
Signed-off-by: Vamsi Krishna Lanka <quic_vamslank@quicinc.com>