SourceLevelDebugPkg/SecPeiDebugAgentLib: Fix duplicate symbol

SourceLevelDebugPkg/SecPeiDebugAgentLib: Fix duplicate symbol

https://bugzilla.tianocore.org/show_bug.cgi?id=573
https://bugzilla.tianocore.org/show_bug.cgi?id=796

The same issue is reported again by GCC. Resend this patch again.
This patch renames the duplicated function name to fix it.

The SecPeiDebugAgentLib uses the global variable
mMemoryDiscoveredNotifyList for a PPI notification on
the Memory Discovered PPI.  This same variable name is
used in the DxeIplPeim for the same PPI notification.

The XCODE5 tool chain detects this duplicate symbol
when the OVMF platform is built with the flag
-D SOURCE_DEBUG_ENABLE.

The fix is to rename this global variable in the
SecPeiDebugAgentLib library.

Cc: Andrew Fish <afish@apple.com>
Cc: Jeff Fan <jeff.fan@intel.com>
Cc: Hao Wu <hao.a.wu@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Michael D Kinney <michael.d.kinney@intel.com>
Reviewed-by: Jeff Fan <jeff.fan@intel.com>
Reviewed-by: Ruiyu Ni <ruiyu.ni@intel.com>
Reviewed-by: Hao Wu <hao.a.wu@intel.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>