MdePkg/SafeString.c: Fix code to be more readable
MdePkg/SafeString.c: Fix code to be more readable

The change doesn't impact the functionality.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Ruiyu Ni <9fa3a6894a36bca79e6a72ad65af5a5702efecd1@intel.com>
Reviewed-by: Hao A Wu <f387b71200577e27ccf5abb090fda0ddd187ec6e@intel.com>

MattDevo/edk2,MattDevo/edk2,MattDevo/edk2,MattDevo/edk2,MattDevo/edk2,MattDevo/edk2,MattDevo/edk2,MattDevo/edk2