MdeModulePkg/Library: Fix typos in comments and variables

- servity -> severity
- TURE -> TRUE
- contiue -> continue
- Pepresentation -> Representation
- suported -> supported
- opints -> points
- sucessfully -> successfully
- hexidecimal -> hexadecimal
- Pacakge -> Package
- Libary -> Library
- successull -> successfully
- reseting -> resetting
- Retrive -> Retrieve
- dirver -> driver
- availible -> available
- chracter -> character
- seperator -> separator

Cc: Feng Tian <feng.tian@intel.com>
Cc: Star Zeng <star.zeng@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Gary Lin <glin@suse.com>
Reviewed-by: Feng Tian <feng.tian@intel.com>
Reviewed-by: Star Zeng <star.zeng@intel.com>

MdeModulePkg/Library/DebugAgentLibNull/DebugAgentLibNull.c

@@ -24,7 +24,7 @@
   function and pass it into InitializeDebugAgent(). InitializeDebugAgent() is
   responsible to invoke the passing-in function at the end of InitializeDebugAgent().
 
-  If the parameter Function is not NULL, Debug Agent Libary instance will invoke it by
+  If the parameter Function is not NULL, Debug Agent Library instance will invoke it by
   passing in the Context to be its parameter.
 
   If Function() is NULL, Debug Agent Library instance will return after setup debug