Fix Context::colorWriteActive to consider all rendertargets

Even in the GLES backend, we support RENDERTARGETS=8. This check only
ever considered the first 4.

Bug: b/126719156
Change-Id: I0084aa005f342f06373c53c007bee33268466b92
Reviewed-on: https://swiftshader-review.googlesource.com/c/25808
Tested-by: Chris Forbes <chrisforbes@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>

src/Device/Context.cpp

diff --git a/src/Device/Context.cpp b/src/Device/Context.cpp
index d4ed3dc..afa3931 100644
--- a/src/Device/Context.cpp
+++ b/src/Device/Context.cpp
@@ -730,9 +730,17 @@
 		}
 	}
 
-	int Context::colorWriteActive()
+	bool Context::colorWriteActive()
 	{
-		return colorWriteActive(0) | colorWriteActive(1) | colorWriteActive(2) | colorWriteActive(3);
+		for (int i = 0; i < RENDERTARGETS; i++)
+		{
+			if (colorWriteActive(i))
+			{
+				return true;
+			}
+		}
+
+		return false;
 	}
 
 	int Context::colorWriteActive(int index)