engines/maxwell_*: Use nested namespace specifiers where applicable

These three source files are the only ones within the engines directory
that don't use nested namespaces. We may as well change these over to
keep things consistent.

src/video_core/engines/maxwell_3d.cpp

@@ -13,8 +13,7 @@
 #include "video_core/renderer_base.h"
 #include "video_core/textures/texture.h"
 
-namespace Tegra {
-namespace Engines {
+namespace Tegra::Engines {
 
 /// First register id that is actually a Macro call.
 constexpr u32 MacroRegistersStart = 0xE00;
@@ -408,5 +407,4 @@ void Maxwell3D::ProcessClearBuffers() {
     rasterizer.Clear();
 }
 
-} // namespace Engines
-} // namespace Tegra
+} // namespace Tegra::Engines

src/video_core/engines/maxwell_compute.cpp

@@ -6,8 +6,7 @@
 #include "core/core.h"
 #include "video_core/engines/maxwell_compute.h"
 
-namespace Tegra {
-namespace Engines {
+namespace Tegra::Engines {
 
 void MaxwellCompute::WriteReg(u32 method, u32 value) {
     ASSERT_MSG(method < Regs::NUM_REGS,
@@ -26,5 +25,4 @@ void MaxwellCompute::WriteReg(u32 method, u32 value) {
     }
 }
 
-} // namespace Engines
-} // namespace Tegra
+} // namespace Tegra::Engines

src/video_core/engines/maxwell_dma.cpp

@@ -7,8 +7,7 @@
 #include "video_core/rasterizer_interface.h"
 #include "video_core/textures/decoders.h"
 
-namespace Tegra {
-namespace Engines {
+namespace Tegra::Engines {
 
 MaxwellDMA::MaxwellDMA(VideoCore::RasterizerInterface& rasterizer, MemoryManager& memory_manager)
     : memory_manager(memory_manager), rasterizer{rasterizer} {}
@@ -119,5 +118,4 @@ void MaxwellDMA::HandleCopy() {
     }
 }
 
-} // namespace Engines
-} // namespace Tegra
+} // namespace Tegra::Engines