AdvancedLogger DxeCore - set mBufferSize if AdvancedLoggerGettLoggerInfo returns NULL (#58)

AdvancedLogger DxeCore - set mBufferSize if AdvancedLoggerGettLoggerInfo returns NULL

## Description

* Update AdvancedLoggerPkg AdvancedLoggerLib DxeCore variant to set mBufferSize if AdvancedLoggerGetLoggerInfo returns NULL.

- [ ] Breaking change?
  - Will this change break pre-existing builds or functionality without action being taken?
  No, this is not a breaking change.

## How This Was Tested

* Verified on Surface Arm platform.

## Integration Instructions

N/A

AdvLoggerPkg/Library/AdvancedLoggerLib/DxeCore/AdvancedLoggerLib.c

@@ -365,6 +365,7 @@ DxeCoreAdvancedLoggerLibConstructor (
       LoggerInfo->LogBufferSize = EFI_PAGES_TO_SIZE (FixedPcdGet32 (PcdAdvancedLoggerPages)) - sizeof (ADVANCED_LOGGER_INFO);
       LoggerInfo->LogCurrent    = LoggerInfo->LogBuffer;
       mMaxAddress               = PA_FROM_PTR (LoggerInfo) + LoggerInfo->LogBufferSize;
+      mBufferSize               = LoggerInfo->LogBufferSize;
     } else {
       DEBUG ((DEBUG_ERROR, "%a: Error allocating Advanced Logger Buffer\n", __FUNCTION__));
     }