Remove gpu feature and third party module gdrcopy

Signed-off-by: Leonardo Carreras <leonardo.carreras@eonerc.rwth-aachen.de>

Author: leonardocarreras

.gitmodules

@@ -7,6 +7,3 @@
 [submodule "fpga/thirdparty/udmabuf"]
 	path = fpga/thirdparty/udmabuf
 	url = https://github.com/ikwzm/udmabuf
-[submodule "fpga/lib/gpu/gdrcopy"]
-	path = fpga/gpu/thirdparty/gdrcopy
-	url = https://github.com/daniel-k/gdrcopy.git

fpga/CMakeLists.txt

@@ -4,16 +4,6 @@
 # SPDX-FileCopyrightText: 2018 Institute for Automation of Complex Power Systems, RWTH Aachen University
 # SPDX-License-Identifier: Apache-2.0
 
-# GPU library is optional, check for CUDA presence
-include(CheckLanguage)
-check_language(CUDA)
-
-if(CMAKE_CUDA_COMPILER)
-    add_subdirectory(gpu)
-else()
-    message("No CUDA support, not building GPU library")
-endif()
-
 include(FindPkgConfig)
 
 set(ENV{PKG_CONFIG_PATH} "$ENV{PKG_CONFIG_PATH}:/usr/local/lib/pkgconfig:/usr/local/lib64/pkgconfig:/usr/local/share/pkgconfig:/usr/lib64/pkgconfig")