MdeModulePkg SmiHandlerProfile: Use fixed data type in data structure

MdeModulePkg SmiHandlerProfile: Use fixed data type in data structure

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=568

Use fixed data type in data structure and make the structure
be natural aligned.
Without this update, the code must assume DXE and SMM are using
same data type (same size of UINTN), but it may be not true at
some case, for example, after standalone SMM feature is enabled.
With this update, the data structure will be phase independent
and convenient for consumer to parse the data.

Cc: Jiewen Yao <jiewen.yao@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Star Zeng <star.zeng@intel.com>
Reviewed-by: Jiewen Yao <jiewen.yao@intel.com>