MdePkg PiPeiCis.h: Add description for notification PPI from SEC
MdePkg PiPeiCis.h: Add description for notification PPI from SEC

This patch is to follow latest (>= 1.5) PI spec to add description
for notification PPI from SEC

Cc: Liming Gao <6480311aeeb4b006862f6d13ebabddc03f51e507@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Star Zeng <5c6bb72efe464613af94e84c05522a361b23844a@intel.com>
Reviewed-by: Liming Gao <6480311aeeb4b006862f6d13ebabddc03f51e507@intel.com>

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