ShellPkg: BcfgDisplayDump(): accumulate errors

ShellPkg: BcfgDisplayDump(): accumulate errors

Don't exit the command immediately when a variable access fails; continue
processing after printing the error message. Let the final return status
reflect any encountered errors.

This patch is intended as a functional improvement.

Cc: Jaben Carsey <jaben.carsey@intel.com>
Cc: Ryan Harkin <ryan.harkin@linaro.org>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Jaben Carsey <jaben.carsey@intel.com>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@19709 6f19259b-4bc3-4df7-8a09-765794883524