video_core: Fix d24r8/s8d24 convert shader build error in moltenvk

src/video_core/host_shaders/convert_d24s8_to_abgr8.frag

@@ -3,16 +3,16 @@
 
 #version 450
 
+precision mediump int;
+precision highp float;
+
 layout(binding = 0) uniform sampler2D depth_tex;
-layout(binding = 1) uniform isampler2D stencil_tex;
+layout(binding = 1) uniform usampler2D stencil_tex;
 
 layout(location = 0) out vec4 color;
 
 void main() {
     ivec2 coord = ivec2(gl_FragCoord.xy);
-    uint depth = uint(textureLod(depth_tex, coord, 0).r * (exp2(24.0) - 1.0f));
-    uint stencil = uint(textureLod(stencil_tex, coord, 0).r);
-
     highp uint depth_val =
         uint(textureLod(depth_tex, coord, 0).r * (exp2(32.0) - 1.0));
     lowp uint stencil_val = textureLod(stencil_tex, coord, 0).r;

src/video_core/host_shaders/convert_s8d24_to_abgr8.frag

@@ -3,16 +3,16 @@
 
 #version 450
 
+precision mediump int;
+precision highp float;
+
 layout(binding = 0) uniform sampler2D depth_tex;
-layout(binding = 1) uniform isampler2D stencil_tex;
+layout(binding = 1) uniform usampler2D stencil_tex;
 
 layout(location = 0) out vec4 color;
 
 void main() {
     ivec2 coord = ivec2(gl_FragCoord.xy);
-    uint depth = uint(textureLod(depth_tex, coord, 0).r * (exp2(24.0) - 1.0f));
-    uint stencil = uint(textureLod(stencil_tex, coord, 0).r);
-
     highp uint depth_val =
         uint(textureLod(depth_tex, coord, 0).r * (exp2(32.0) - 1.0));
     lowp uint stencil_val = textureLod(stencil_tex, coord, 0).r;