MdeModulePkg:Avoid ASSERT in HiiConfigRoutingRouteConfig

Add error handling code to enhance the code,the driver may not install
the ConfigAccess protocol,so should not just ASSERT here.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Dandan Bi <dandan.bi@intel.com>
Reviewed-by: Eric Dong <eric.dong@intel.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@19590 6f19259b-4bc3-4df7-8a09-765794883524