gl_shader_util: Cleanup header file + add docstring.

src/video_core/renderer_opengl/gl_shader_util.h

@@ -14,6 +14,12 @@ enum Attributes {
     ATTRIBUTE_TEXCOORDS = 2,
 };
 
-GLuint LoadProgram(const char* vertex_file_path, const char* fragment_file_path);
+/**
+ * Utility function to create and compile an OpenGL GLSL shader program (vertex + fragment shader)
+ * @param vertex_shader String of the GLSL vertex shader program
+ * @param fragment_shader String of the GLSL fragment shader program
+ * @returns Handle of the newly created OpenGL shader object
+ */
+GLuint LoadProgram(const char* vertex_shader, const char* fragment_shader);
 
 } // namespace