GS: Clamp pow conColor to always be positive.

Fixes warning:
warning X3571: pow(f, e) will not work for negative f,
use abs(f) or conditionally handle negative values if you expect them

Author: lightningterror

bin/resources/shaders/dx11/shadeboost.fx

@@ -37,7 +37,7 @@ float4 ContrastSaturationBrightness(float4 color) // Ported to HLSL
 	float3 conColor = lerp(AvgLumin, satColor, con);
 
 	float3 csb = conColor;
-	csb = pow(csb, 1.0 / gam);
+	csb = pow(max(csb, 0.0), 1.0 / gam);
 	color.rgb = csb;
 	return color;
 }

bin/resources/shaders/opengl/shadeboost.glsl

@@ -47,7 +47,7 @@ vec4 ContrastSaturationBrightness(vec4 color)
 	vec3 conColor = mix(AvgLumin, satColor, con);
 
 	vec3 csb = conColor;
-	csb = pow(csb, vec3(1.0 / gam));
+	csb = pow(max(csb, 0.0), vec3(1.0 / gam));
 	color.rgb = csb;
 
 	return color;

bin/resources/shaders/vulkan/shadeboost.glsl

@@ -61,7 +61,7 @@ vec4 ContrastSaturationBrightness(vec4 color)
     vec3 conColor = mix(AvgLumin, satColor, con);
 
     vec3 csb = conColor;
-    csb = pow(csb, vec3(1.0 / gam));
+    csb = pow(max(csb, 0.0), vec3(1.0 / gam));
     color.rgb = csb;
     return color;
 }

pcsx2/GS/Renderers/Metal/convert.metal

@@ -547,7 +547,7 @@ fragment float4 ps_shadeboost(float4 p [[position]], DirectReadTextureIn<float>
 	float3 satColor = mix(intensity, brtColor, sat);
 	float3 conColor = mix(AvgLumin, satColor, con);
 
-	float3 csb = pow(conColor, float3(1.0 / gam));
+	float3 csb = pow(max(conColor, 0.0), 1.0 / gam);
 
 	return float4(csb, 1);
 }

pcsx2/ShaderCacheVersion.h

@@ -3,4 +3,4 @@
 
 /// Version number for GS and other shaders. Increment whenever any of the contents of the
 /// shaders change, to invalidate the cache.
-static constexpr u32 SHADER_CACHE_VERSION = 72;
+static constexpr u32 SHADER_CACHE_VERSION = 73;