MdePkg/BaseLib: Remove the unnecessary '_' before library APIs in ASM/NASM

MdePkg/BaseLib: Remove the unnecessary '_' before library APIs in ASM/NASM

The leading underscore (i.e. '_') before the names of some BaseLib library
API in ASM/NASM files is unnecessary. It will cause link error with GCC
tool chains.

Cc: Liming Gao <liming.gao@intel.com>
Cc: Michael Kinney <michael.d.kinney@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Hao Wu <hao.a.wu@intel.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>