Fixed logic related to DxeCore only advanced logger (#359)

## Description

When using advanced logger starting from DxeCore, the library
constructor will allocate space for the advanced logger buffer.
When this allocation takes place, the associated global variable
`mMaxAddress` will be created to specify the last address for the log
buffer.

In the DxeCore case, the calculation for `mMaxAddress` did not take into
account the size of the `ADVANCED_LOGGER_INFO` structure that is at the
start of the buffer, resulting in an inconsistent address between
`mMaxAddress` and `LoggerInfo->LogBuffer + LoggerInfo->LogBufferSize`

All other instances of this code use `LoggerInfo->LogBuffer +
LoggerInfo->LogBufferSize`, so change DxeCore library instance to use
the same logic as other library instances.


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## How This Was Tested
Found by setting debug messages to such a high level that the end of the
buffer was reached, resulting in incorrect checks of `mMaxAddress`
overwriting the end of the buffer.

Incorrect logic was tripped up in `ValidateInfoBlock()` where
`mMaxAddress` would cause a return of `false`, which in turn would
result in NULL being returned from an arbitrary call to
`AdvancedLoggerGetLoggerInfo`.

## Integration Instructions
n/a

AdvLoggerPkg/Library/AdvancedLoggerLib/DxeCore/AdvancedLoggerLib.c

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