MdePkg: MmCommunication2: Update MM communicate2 function description

MdePkg: MmCommunication2: Update MM communicate2 function description

Current MM communicate2 function definition described input arguments
`CommBufferPhysical`, `CommBufferVirtual` and `CommSize` as input only,
which mismatches with the "input and output type" as in PI specification.

This change updated function descriptions of MM communite2 definition to
match input argument types.

Cc: Michael D Kinney <michael.d.kinney@intel.com>
Cc: Liming Gao <gaoliming@byosoft.com.cn>
Cc: Zhiguang Liu <zhiguang.liu@intel.com>
Signed-off-by: Kun Qin <kuqin12@gmail.com>
Reviewed-by: Liming Gao <gaoliming@byosoft.com.cn>