ShellPkg: Fix wrong return status for Ifconfig.c

ShellPkg: Fix wrong return status for Ifconfig.c

The Ifconfig command handler tries to return an EFI_STATUS when
the return type should be SHELL_STATUS.

Cc: Cohen Eugene <eugene@hp.com>
Cc: Carsey Jaben <jaben.carsey@intel.com>
Cc: Ye Ting <ting.ye@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Jiaxin Wu <jiaxin.wu@intel.com>
Reviewed-by: Jaben Carsey <jaben.carsey@intel.com>
Reviewed-by: Ye Ting <ting.ye@intel.com>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@19110 6f19259b-4bc3-4df7-8a09-765794883524