[loco] Rename pad.test.cpp file (#7952)

This commit renames pad.test.cpp file to Padding2D.test.cpp.

Signed-off-by: seongwoo <sw4670.chae@samsung.com>

diff --git a/compiler/loco/src/IR/Pad.test.cpp b/compiler/loco/src/IR/Padding2D.test.cpp
similarity index 100%
rename from compiler/loco/src/IR/Pad.test.cpp
rename to compiler/loco/src/IR/Padding2D.test.cpp