.pytool/EccCheck: Rename edk2_path as workspace_path

.pytool/EccCheck: Rename edk2_path as workspace_path

The edk2 path and the workspace path are identical when running
Ecc on edk2. When running Ecc on another repository
(e.g.: edk2-platforms with edk2 as a submodule of edk2-platforms),
these directories are different. Indeed, in the latter configuration,
Ecc must run git commands on the tested repository, i.e. the workspace
directory, edk2-platforms.

Thus, rename edk2_path as workspace_path.

Cc: Sean Brogan <sean.brogan@microsoft.com>
Cc: Bret Barkelew <Bret.Barkelew@microsoft.com>
Cc: Michael D Kinney <michael.d.kinney@intel.com>
Cc: Liming Gao <gaoliming@byosoft.com.cn>
Cc: Sami Mujawar <sami.mujawar@arm.com>
Signed-off-by: Pierre Gondois <Pierre.Gondois@arm.com>
Reviewed-by: Liming Gao <gaoliming@byosoft.com.cn>