StandaloneMmPkg: Fix spell check reported errors

StandaloneMmPkg: Fix spell check reported errors

Bugzilla: 3150 (https://bugzilla.tianocore.org/show_bug.cgi?id=3150)

Fix the spelling mistakes reported by the spell check utility
that is run as part of the Core CI.

Signed-off-by: Sami Mujawar <sami.mujawar@arm.com>
Acked-by: Jiewen Yao <Jiewen.yao@intel.com>
Acked-by: Ard Biesheuvel <ard.biesheuvel@arm.com>
Reviewed-by: Liming Gao <gaoliming@byosoft.com.cn>